1------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3------------------------------------------------------------------------------ 4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 5 Bodo Bauer <bb@ricochet.net> 6 72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 9------------------------------------------------------------------------------ 10Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12------------------------------------------------------------------------------ 13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 14 15Table of Contents 16----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 37 score 38 3.2 /proc/<pid>/oom_score - Display current oom-killer score 39 3.3 /proc/<pid>/io - Display the IO accounting fields 40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 41 3.5 /proc/<pid>/mountinfo - Information about mounts 42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 43 3.7 /proc/<pid>/task/<tid>/children - Information about task children 44 45 4 Configuring procfs 46 4.1 Mount options 47 48------------------------------------------------------------------------------ 49Preface 50------------------------------------------------------------------------------ 51 520.1 Introduction/Credits 53------------------------ 54 55This documentation is part of a soon (or so we hope) to be released book on 56the SuSE Linux distribution. As there is no complete documentation for the 57/proc file system and we've used many freely available sources to write these 58chapters, it seems only fair to give the work back to the Linux community. 59This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 60afraid it's still far from complete, but we hope it will be useful. As far as 61we know, it is the first 'all-in-one' document about the /proc file system. It 62is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 63SPARC, AXP, etc., features, you probably won't find what you are looking for. 64It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 65additions and patches are welcome and will be added to this document if you 66mail them to Bodo. 67 68We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 69other people for help compiling this documentation. We'd also like to extend a 70special thank you to Andi Kleen for documentation, which we relied on heavily 71to create this document, as well as the additional information he provided. 72Thanks to everybody else who contributed source or docs to the Linux kernel 73and helped create a great piece of software... :) 74 75If you have any comments, corrections or additions, please don't hesitate to 76contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 77document. 78 79The latest version of this document is available online at 80http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 81 82If the above direction does not works for you, you could try the kernel 83mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 84comandante@zaralinux.com. 85 860.2 Legal Stuff 87--------------- 88 89We don't guarantee the correctness of this document, and if you come to us 90complaining about how you screwed up your system because of incorrect 91documentation, we won't feel responsible... 92 93------------------------------------------------------------------------------ 94CHAPTER 1: COLLECTING SYSTEM INFORMATION 95------------------------------------------------------------------------------ 96 97------------------------------------------------------------------------------ 98In This Chapter 99------------------------------------------------------------------------------ 100* Investigating the properties of the pseudo file system /proc and its 101 ability to provide information on the running Linux system 102* Examining /proc's structure 103* Uncovering various information about the kernel and the processes running 104 on the system 105------------------------------------------------------------------------------ 106 107 108The proc file system acts as an interface to internal data structures in the 109kernel. It can be used to obtain information about the system and to change 110certain kernel parameters at runtime (sysctl). 111 112First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 113show you how you can use /proc/sys to change settings. 114 1151.1 Process-Specific Subdirectories 116----------------------------------- 117 118The directory /proc contains (among other things) one subdirectory for each 119process running on the system, which is named after the process ID (PID). 120 121The link self points to the process reading the file system. Each process 122subdirectory has the entries listed in Table 1-1. 123 124 125Table 1-1: Process specific entries in /proc 126.............................................................................. 127 File Content 128 clear_refs Clears page referenced bits shown in smaps output 129 cmdline Command line arguments 130 cpu Current and last cpu in which it was executed (2.4)(smp) 131 cwd Link to the current working directory 132 environ Values of environment variables 133 exe Link to the executable of this process 134 fd Directory, which contains all file descriptors 135 maps Memory maps to executables and library files (2.4) 136 mem Memory held by this process 137 root Link to the root directory of this process 138 stat Process status 139 statm Process memory status information 140 status Process status in human readable form 141 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan 142 pagemap Page table 143 stack Report full stack trace, enable via CONFIG_STACKTRACE 144 smaps a extension based on maps, showing the memory consumption of 145 each mapping 146.............................................................................. 147 148For example, to get the status information of a process, all you have to do is 149read the file /proc/PID/status: 150 151 >cat /proc/self/status 152 Name: cat 153 State: R (running) 154 Tgid: 5452 155 Pid: 5452 156 PPid: 743 157 TracerPid: 0 (2.4) 158 Uid: 501 501 501 501 159 Gid: 100 100 100 100 160 FDSize: 256 161 Groups: 100 14 16 162 VmPeak: 5004 kB 163 VmSize: 5004 kB 164 VmLck: 0 kB 165 VmHWM: 476 kB 166 VmRSS: 476 kB 167 VmData: 156 kB 168 VmStk: 88 kB 169 VmExe: 68 kB 170 VmLib: 1412 kB 171 VmPTE: 20 kb 172 VmSwap: 0 kB 173 Threads: 1 174 SigQ: 0/28578 175 SigPnd: 0000000000000000 176 ShdPnd: 0000000000000000 177 SigBlk: 0000000000000000 178 SigIgn: 0000000000000000 179 SigCgt: 0000000000000000 180 CapInh: 00000000fffffeff 181 CapPrm: 0000000000000000 182 CapEff: 0000000000000000 183 CapBnd: ffffffffffffffff 184 voluntary_ctxt_switches: 0 185 nonvoluntary_ctxt_switches: 1 186 187This shows you nearly the same information you would get if you viewed it with 188the ps command. In fact, ps uses the proc file system to obtain its 189information. But you get a more detailed view of the process by reading the 190file /proc/PID/status. It fields are described in table 1-2. 191 192The statm file contains more detailed information about the process 193memory usage. Its seven fields are explained in Table 1-3. The stat file 194contains details information about the process itself. Its fields are 195explained in Table 1-4. 196 197(for SMP CONFIG users) 198For making accounting scalable, RSS related information are handled in 199asynchronous manner and the vaule may not be very precise. To see a precise 200snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 201It's slow but very precise. 202 203Table 1-2: Contents of the status files (as of 2.6.30-rc7) 204.............................................................................. 205 Field Content 206 Name filename of the executable 207 State state (R is running, S is sleeping, D is sleeping 208 in an uninterruptible wait, Z is zombie, 209 T is traced or stopped) 210 Tgid thread group ID 211 Pid process id 212 PPid process id of the parent process 213 TracerPid PID of process tracing this process (0 if not) 214 Uid Real, effective, saved set, and file system UIDs 215 Gid Real, effective, saved set, and file system GIDs 216 FDSize number of file descriptor slots currently allocated 217 Groups supplementary group list 218 VmPeak peak virtual memory size 219 VmSize total program size 220 VmLck locked memory size 221 VmHWM peak resident set size ("high water mark") 222 VmRSS size of memory portions 223 VmData size of data, stack, and text segments 224 VmStk size of data, stack, and text segments 225 VmExe size of text segment 226 VmLib size of shared library code 227 VmPTE size of page table entries 228 VmSwap size of swap usage (the number of referred swapents) 229 Threads number of threads 230 SigQ number of signals queued/max. number for queue 231 SigPnd bitmap of pending signals for the thread 232 ShdPnd bitmap of shared pending signals for the process 233 SigBlk bitmap of blocked signals 234 SigIgn bitmap of ignored signals 235 SigCgt bitmap of catched signals 236 CapInh bitmap of inheritable capabilities 237 CapPrm bitmap of permitted capabilities 238 CapEff bitmap of effective capabilities 239 CapBnd bitmap of capabilities bounding set 240 Cpus_allowed mask of CPUs on which this process may run 241 Cpus_allowed_list Same as previous, but in "list format" 242 Mems_allowed mask of memory nodes allowed to this process 243 Mems_allowed_list Same as previous, but in "list format" 244 voluntary_ctxt_switches number of voluntary context switches 245 nonvoluntary_ctxt_switches number of non voluntary context switches 246.............................................................................. 247 248Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 249.............................................................................. 250 Field Content 251 size total program size (pages) (same as VmSize in status) 252 resident size of memory portions (pages) (same as VmRSS in status) 253 shared number of pages that are shared (i.e. backed by a file) 254 trs number of pages that are 'code' (not including libs; broken, 255 includes data segment) 256 lrs number of pages of library (always 0 on 2.6) 257 drs number of pages of data/stack (including libs; broken, 258 includes library text) 259 dt number of dirty pages (always 0 on 2.6) 260.............................................................................. 261 262 263Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 264.............................................................................. 265 Field Content 266 pid process id 267 tcomm filename of the executable 268 state state (R is running, S is sleeping, D is sleeping in an 269 uninterruptible wait, Z is zombie, T is traced or stopped) 270 ppid process id of the parent process 271 pgrp pgrp of the process 272 sid session id 273 tty_nr tty the process uses 274 tty_pgrp pgrp of the tty 275 flags task flags 276 min_flt number of minor faults 277 cmin_flt number of minor faults with child's 278 maj_flt number of major faults 279 cmaj_flt number of major faults with child's 280 utime user mode jiffies 281 stime kernel mode jiffies 282 cutime user mode jiffies with child's 283 cstime kernel mode jiffies with child's 284 priority priority level 285 nice nice level 286 num_threads number of threads 287 it_real_value (obsolete, always 0) 288 start_time time the process started after system boot 289 vsize virtual memory size 290 rss resident set memory size 291 rsslim current limit in bytes on the rss 292 start_code address above which program text can run 293 end_code address below which program text can run 294 start_stack address of the start of the main process stack 295 esp current value of ESP 296 eip current value of EIP 297 pending bitmap of pending signals 298 blocked bitmap of blocked signals 299 sigign bitmap of ignored signals 300 sigcatch bitmap of catched signals 301 wchan address where process went to sleep 302 0 (place holder) 303 0 (place holder) 304 exit_signal signal to send to parent thread on exit 305 task_cpu which CPU the task is scheduled on 306 rt_priority realtime priority 307 policy scheduling policy (man sched_setscheduler) 308 blkio_ticks time spent waiting for block IO 309 gtime guest time of the task in jiffies 310 cgtime guest time of the task children in jiffies 311 start_data address above which program data+bss is placed 312 end_data address below which program data+bss is placed 313 start_brk address above which program heap can be expanded with brk() 314 arg_start address above which program command line is placed 315 arg_end address below which program command line is placed 316 env_start address above which program environment is placed 317 env_end address below which program environment is placed 318 exit_code the thread's exit_code in the form reported by the waitpid system call 319.............................................................................. 320 321The /proc/PID/maps file containing the currently mapped memory regions and 322their access permissions. 323 324The format is: 325 326address perms offset dev inode pathname 327 32808048000-08049000 r-xp 00000000 03:00 8312 /opt/test 32908049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3300804a000-0806b000 rw-p 00000000 00:00 0 [heap] 331a7cb1000-a7cb2000 ---p 00000000 00:00 0 332a7cb2000-a7eb2000 rw-p 00000000 00:00 0 333a7eb2000-a7eb3000 ---p 00000000 00:00 0 334a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001] 335a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 336a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 337a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 338a800b000-a800e000 rw-p 00000000 00:00 0 339a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 340a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 341a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 342a8024000-a8027000 rw-p 00000000 00:00 0 343a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 344a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 345a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 346aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 347ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 348 349where "address" is the address space in the process that it occupies, "perms" 350is a set of permissions: 351 352 r = read 353 w = write 354 x = execute 355 s = shared 356 p = private (copy on write) 357 358"offset" is the offset into the mapping, "dev" is the device (major:minor), and 359"inode" is the inode on that device. 0 indicates that no inode is associated 360with the memory region, as the case would be with BSS (uninitialized data). 361The "pathname" shows the name associated file for this mapping. If the mapping 362is not associated with a file: 363 364 [heap] = the heap of the program 365 [stack] = the stack of the main process 366 [stack:1001] = the stack of the thread with tid 1001 367 [vdso] = the "virtual dynamic shared object", 368 the kernel system call handler 369 370 or if empty, the mapping is anonymous. 371 372The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint 373of the individual tasks of a process. In this file you will see a mapping marked 374as [stack] if that task sees it as a stack. This is a key difference from the 375content of /proc/PID/maps, where you will see all mappings that are being used 376as stack by all of those tasks. Hence, for the example above, the task-level 377map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this: 378 37908048000-08049000 r-xp 00000000 03:00 8312 /opt/test 38008049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3810804a000-0806b000 rw-p 00000000 00:00 0 [heap] 382a7cb1000-a7cb2000 ---p 00000000 00:00 0 383a7cb2000-a7eb2000 rw-p 00000000 00:00 0 384a7eb2000-a7eb3000 ---p 00000000 00:00 0 385a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack] 386a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 387a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 388a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 389a800b000-a800e000 rw-p 00000000 00:00 0 390a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 391a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 392a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 393a8024000-a8027000 rw-p 00000000 00:00 0 394a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 395a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 396a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 397aff35000-aff4a000 rw-p 00000000 00:00 0 398ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 399 400The /proc/PID/smaps is an extension based on maps, showing the memory 401consumption for each of the process's mappings. For each of mappings there 402is a series of lines such as the following: 403 40408048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 405Size: 1084 kB 406Rss: 892 kB 407Pss: 374 kB 408Shared_Clean: 892 kB 409Shared_Dirty: 0 kB 410Private_Clean: 0 kB 411Private_Dirty: 0 kB 412Referenced: 892 kB 413Anonymous: 0 kB 414Swap: 0 kB 415KernelPageSize: 4 kB 416MMUPageSize: 4 kB 417Locked: 374 kB 418 419The first of these lines shows the same information as is displayed for the 420mapping in /proc/PID/maps. The remaining lines show the size of the mapping 421(size), the amount of the mapping that is currently resident in RAM (RSS), the 422process' proportional share of this mapping (PSS), the number of clean and 423dirty private pages in the mapping. Note that even a page which is part of a 424MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used 425by only one process, is accounted as private and not as shared. "Referenced" 426indicates the amount of memory currently marked as referenced or accessed. 427"Anonymous" shows the amount of memory that does not belong to any file. Even 428a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 429and a page is modified, the file page is replaced by a private anonymous copy. 430"Swap" shows how much would-be-anonymous memory is also used, but out on 431swap. 432 433This file is only present if the CONFIG_MMU kernel configuration option is 434enabled. 435 436The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 437bits on both physical and virtual pages associated with a process. 438To clear the bits for all the pages associated with the process 439 > echo 1 > /proc/PID/clear_refs 440 441To clear the bits for the anonymous pages associated with the process 442 > echo 2 > /proc/PID/clear_refs 443 444To clear the bits for the file mapped pages associated with the process 445 > echo 3 > /proc/PID/clear_refs 446Any other value written to /proc/PID/clear_refs will have no effect. 447 448The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 449using /proc/kpageflags and number of times a page is mapped using 450/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. 451 4521.2 Kernel data 453--------------- 454 455Similar to the process entries, the kernel data files give information about 456the running kernel. The files used to obtain this information are contained in 457/proc and are listed in Table 1-5. Not all of these will be present in your 458system. It depends on the kernel configuration and the loaded modules, which 459files are there, and which are missing. 460 461Table 1-5: Kernel info in /proc 462.............................................................................. 463 File Content 464 apm Advanced power management info 465 buddyinfo Kernel memory allocator information (see text) (2.5) 466 bus Directory containing bus specific information 467 cmdline Kernel command line 468 cpuinfo Info about the CPU 469 devices Available devices (block and character) 470 dma Used DMS channels 471 filesystems Supported filesystems 472 driver Various drivers grouped here, currently rtc (2.4) 473 execdomains Execdomains, related to security (2.4) 474 fb Frame Buffer devices (2.4) 475 fs File system parameters, currently nfs/exports (2.4) 476 ide Directory containing info about the IDE subsystem 477 interrupts Interrupt usage 478 iomem Memory map (2.4) 479 ioports I/O port usage 480 irq Masks for irq to cpu affinity (2.4)(smp?) 481 isapnp ISA PnP (Plug&Play) Info (2.4) 482 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 483 kmsg Kernel messages 484 ksyms Kernel symbol table 485 loadavg Load average of last 1, 5 & 15 minutes 486 locks Kernel locks 487 meminfo Memory info 488 misc Miscellaneous 489 modules List of loaded modules 490 mounts Mounted filesystems 491 net Networking info (see text) 492 pagetypeinfo Additional page allocator information (see text) (2.5) 493 partitions Table of partitions known to the system 494 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 495 decoupled by lspci (2.4) 496 rtc Real time clock 497 scsi SCSI info (see text) 498 slabinfo Slab pool info 499 softirqs softirq usage 500 stat Overall statistics 501 swaps Swap space utilization 502 sys See chapter 2 503 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 504 tty Info of tty drivers 505 uptime System uptime 506 version Kernel version 507 video bttv info of video resources (2.4) 508 vmallocinfo Show vmalloced areas 509.............................................................................. 510 511You can, for example, check which interrupts are currently in use and what 512they are used for by looking in the file /proc/interrupts: 513 514 > cat /proc/interrupts 515 CPU0 516 0: 8728810 XT-PIC timer 517 1: 895 XT-PIC keyboard 518 2: 0 XT-PIC cascade 519 3: 531695 XT-PIC aha152x 520 4: 2014133 XT-PIC serial 521 5: 44401 XT-PIC pcnet_cs 522 8: 2 XT-PIC rtc 523 11: 8 XT-PIC i82365 524 12: 182918 XT-PIC PS/2 Mouse 525 13: 1 XT-PIC fpu 526 14: 1232265 XT-PIC ide0 527 15: 7 XT-PIC ide1 528 NMI: 0 529 530In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 531output of a SMP machine): 532 533 > cat /proc/interrupts 534 535 CPU0 CPU1 536 0: 1243498 1214548 IO-APIC-edge timer 537 1: 8949 8958 IO-APIC-edge keyboard 538 2: 0 0 XT-PIC cascade 539 5: 11286 10161 IO-APIC-edge soundblaster 540 8: 1 0 IO-APIC-edge rtc 541 9: 27422 27407 IO-APIC-edge 3c503 542 12: 113645 113873 IO-APIC-edge PS/2 Mouse 543 13: 0 0 XT-PIC fpu 544 14: 22491 24012 IO-APIC-edge ide0 545 15: 2183 2415 IO-APIC-edge ide1 546 17: 30564 30414 IO-APIC-level eth0 547 18: 177 164 IO-APIC-level bttv 548 NMI: 2457961 2457959 549 LOC: 2457882 2457881 550 ERR: 2155 551 552NMI is incremented in this case because every timer interrupt generates a NMI 553(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 554 555LOC is the local interrupt counter of the internal APIC of every CPU. 556 557ERR is incremented in the case of errors in the IO-APIC bus (the bus that 558connects the CPUs in a SMP system. This means that an error has been detected, 559the IO-APIC automatically retry the transmission, so it should not be a big 560problem, but you should read the SMP-FAQ. 561 562In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 563/proc/interrupts to display every IRQ vector in use by the system, not 564just those considered 'most important'. The new vectors are: 565 566 THR -- interrupt raised when a machine check threshold counter 567 (typically counting ECC corrected errors of memory or cache) exceeds 568 a configurable threshold. Only available on some systems. 569 570 TRM -- a thermal event interrupt occurs when a temperature threshold 571 has been exceeded for the CPU. This interrupt may also be generated 572 when the temperature drops back to normal. 573 574 SPU -- a spurious interrupt is some interrupt that was raised then lowered 575 by some IO device before it could be fully processed by the APIC. Hence 576 the APIC sees the interrupt but does not know what device it came from. 577 For this case the APIC will generate the interrupt with a IRQ vector 578 of 0xff. This might also be generated by chipset bugs. 579 580 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 581 sent from one CPU to another per the needs of the OS. Typically, 582 their statistics are used by kernel developers and interested users to 583 determine the occurrence of interrupts of the given type. 584 585The above IRQ vectors are displayed only when relevant. For example, 586the threshold vector does not exist on x86_64 platforms. Others are 587suppressed when the system is a uniprocessor. As of this writing, only 588i386 and x86_64 platforms support the new IRQ vector displays. 589 590Of some interest is the introduction of the /proc/irq directory to 2.4. 591It could be used to set IRQ to CPU affinity, this means that you can "hook" an 592IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 593irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 594prof_cpu_mask. 595 596For example 597 > ls /proc/irq/ 598 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 599 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 600 > ls /proc/irq/0/ 601 smp_affinity 602 603smp_affinity is a bitmask, in which you can specify which CPUs can handle the 604IRQ, you can set it by doing: 605 606 > echo 1 > /proc/irq/10/smp_affinity 607 608This means that only the first CPU will handle the IRQ, but you can also echo 6095 which means that only the first and fourth CPU can handle the IRQ. 610 611The contents of each smp_affinity file is the same by default: 612 613 > cat /proc/irq/0/smp_affinity 614 ffffffff 615 616There is an alternate interface, smp_affinity_list which allows specifying 617a cpu range instead of a bitmask: 618 619 > cat /proc/irq/0/smp_affinity_list 620 1024-1031 621 622The default_smp_affinity mask applies to all non-active IRQs, which are the 623IRQs which have not yet been allocated/activated, and hence which lack a 624/proc/irq/[0-9]* directory. 625 626The node file on an SMP system shows the node to which the device using the IRQ 627reports itself as being attached. This hardware locality information does not 628include information about any possible driver locality preference. 629 630prof_cpu_mask specifies which CPUs are to be profiled by the system wide 631profiler. Default value is ffffffff (all cpus if there are only 32 of them). 632 633The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 634between all the CPUs which are allowed to handle it. As usual the kernel has 635more info than you and does a better job than you, so the defaults are the 636best choice for almost everyone. [Note this applies only to those IO-APIC's 637that support "Round Robin" interrupt distribution.] 638 639There are three more important subdirectories in /proc: net, scsi, and sys. 640The general rule is that the contents, or even the existence of these 641directories, depend on your kernel configuration. If SCSI is not enabled, the 642directory scsi may not exist. The same is true with the net, which is there 643only when networking support is present in the running kernel. 644 645The slabinfo file gives information about memory usage at the slab level. 646Linux uses slab pools for memory management above page level in version 2.2. 647Commonly used objects have their own slab pool (such as network buffers, 648directory cache, and so on). 649 650.............................................................................. 651 652> cat /proc/buddyinfo 653 654Node 0, zone DMA 0 4 5 4 4 3 ... 655Node 0, zone Normal 1 0 0 1 101 8 ... 656Node 0, zone HighMem 2 0 0 1 1 0 ... 657 658External fragmentation is a problem under some workloads, and buddyinfo is a 659useful tool for helping diagnose these problems. Buddyinfo will give you a 660clue as to how big an area you can safely allocate, or why a previous 661allocation failed. 662 663Each column represents the number of pages of a certain order which are 664available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 665ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 666available in ZONE_NORMAL, etc... 667 668More information relevant to external fragmentation can be found in 669pagetypeinfo. 670 671> cat /proc/pagetypeinfo 672Page block order: 9 673Pages per block: 512 674 675Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 676Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 677Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 678Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 679Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 680Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 681Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 682Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 683Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 684Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 685Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 686 687Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 688Node 0, zone DMA 2 0 5 1 0 689Node 0, zone DMA32 41 6 967 2 0 690 691Fragmentation avoidance in the kernel works by grouping pages of different 692migrate types into the same contiguous regions of memory called page blocks. 693A page block is typically the size of the default hugepage size e.g. 2MB on 694X86-64. By keeping pages grouped based on their ability to move, the kernel 695can reclaim pages within a page block to satisfy a high-order allocation. 696 697The pagetypinfo begins with information on the size of a page block. It 698then gives the same type of information as buddyinfo except broken down 699by migrate-type and finishes with details on how many page blocks of each 700type exist. 701 702If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 703from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can 704make an estimate of the likely number of huge pages that can be allocated 705at a given point in time. All the "Movable" blocks should be allocatable 706unless memory has been mlock()'d. Some of the Reclaimable blocks should 707also be allocatable although a lot of filesystem metadata may have to be 708reclaimed to achieve this. 709 710.............................................................................. 711 712meminfo: 713 714Provides information about distribution and utilization of memory. This 715varies by architecture and compile options. The following is from a 71616GB PIII, which has highmem enabled. You may not have all of these fields. 717 718> cat /proc/meminfo 719 720The "Locked" indicates whether the mapping is locked in memory or not. 721 722 723MemTotal: 16344972 kB 724MemFree: 13634064 kB 725Buffers: 3656 kB 726Cached: 1195708 kB 727SwapCached: 0 kB 728Active: 891636 kB 729Inactive: 1077224 kB 730HighTotal: 15597528 kB 731HighFree: 13629632 kB 732LowTotal: 747444 kB 733LowFree: 4432 kB 734SwapTotal: 0 kB 735SwapFree: 0 kB 736Dirty: 968 kB 737Writeback: 0 kB 738AnonPages: 861800 kB 739Mapped: 280372 kB 740Slab: 284364 kB 741SReclaimable: 159856 kB 742SUnreclaim: 124508 kB 743PageTables: 24448 kB 744NFS_Unstable: 0 kB 745Bounce: 0 kB 746WritebackTmp: 0 kB 747CommitLimit: 7669796 kB 748Committed_AS: 100056 kB 749VmallocTotal: 112216 kB 750VmallocUsed: 428 kB 751VmallocChunk: 111088 kB 752AnonHugePages: 49152 kB 753 754 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 755 bits and the kernel binary code) 756 MemFree: The sum of LowFree+HighFree 757 Buffers: Relatively temporary storage for raw disk blocks 758 shouldn't get tremendously large (20MB or so) 759 Cached: in-memory cache for files read from the disk (the 760 pagecache). Doesn't include SwapCached 761 SwapCached: Memory that once was swapped out, is swapped back in but 762 still also is in the swapfile (if memory is needed it 763 doesn't need to be swapped out AGAIN because it is already 764 in the swapfile. This saves I/O) 765 Active: Memory that has been used more recently and usually not 766 reclaimed unless absolutely necessary. 767 Inactive: Memory which has been less recently used. It is more 768 eligible to be reclaimed for other purposes 769 HighTotal: 770 HighFree: Highmem is all memory above ~860MB of physical memory 771 Highmem areas are for use by userspace programs, or 772 for the pagecache. The kernel must use tricks to access 773 this memory, making it slower to access than lowmem. 774 LowTotal: 775 LowFree: Lowmem is memory which can be used for everything that 776 highmem can be used for, but it is also available for the 777 kernel's use for its own data structures. Among many 778 other things, it is where everything from the Slab is 779 allocated. Bad things happen when you're out of lowmem. 780 SwapTotal: total amount of swap space available 781 SwapFree: Memory which has been evicted from RAM, and is temporarily 782 on the disk 783 Dirty: Memory which is waiting to get written back to the disk 784 Writeback: Memory which is actively being written back to the disk 785 AnonPages: Non-file backed pages mapped into userspace page tables 786AnonHugePages: Non-file backed huge pages mapped into userspace page tables 787 Mapped: files which have been mmaped, such as libraries 788 Slab: in-kernel data structures cache 789SReclaimable: Part of Slab, that might be reclaimed, such as caches 790 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 791 PageTables: amount of memory dedicated to the lowest level of page 792 tables. 793NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 794 storage 795 Bounce: Memory used for block device "bounce buffers" 796WritebackTmp: Memory used by FUSE for temporary writeback buffers 797 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 798 this is the total amount of memory currently available to 799 be allocated on the system. This limit is only adhered to 800 if strict overcommit accounting is enabled (mode 2 in 801 'vm.overcommit_memory'). 802 The CommitLimit is calculated with the following formula: 803 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap 804 For example, on a system with 1G of physical RAM and 7G 805 of swap with a `vm.overcommit_ratio` of 30 it would 806 yield a CommitLimit of 7.3G. 807 For more details, see the memory overcommit documentation 808 in vm/overcommit-accounting. 809Committed_AS: The amount of memory presently allocated on the system. 810 The committed memory is a sum of all of the memory which 811 has been allocated by processes, even if it has not been 812 "used" by them as of yet. A process which malloc()'s 1G 813 of memory, but only touches 300M of it will only show up 814 as using 300M of memory even if it has the address space 815 allocated for the entire 1G. This 1G is memory which has 816 been "committed" to by the VM and can be used at any time 817 by the allocating application. With strict overcommit 818 enabled on the system (mode 2 in 'vm.overcommit_memory'), 819 allocations which would exceed the CommitLimit (detailed 820 above) will not be permitted. This is useful if one needs 821 to guarantee that processes will not fail due to lack of 822 memory once that memory has been successfully allocated. 823VmallocTotal: total size of vmalloc memory area 824 VmallocUsed: amount of vmalloc area which is used 825VmallocChunk: largest contiguous block of vmalloc area which is free 826 827.............................................................................. 828 829vmallocinfo: 830 831Provides information about vmalloced/vmaped areas. One line per area, 832containing the virtual address range of the area, size in bytes, 833caller information of the creator, and optional information depending 834on the kind of area : 835 836 pages=nr number of pages 837 phys=addr if a physical address was specified 838 ioremap I/O mapping (ioremap() and friends) 839 vmalloc vmalloc() area 840 vmap vmap()ed pages 841 user VM_USERMAP area 842 vpages buffer for pages pointers was vmalloced (huge area) 843 N<node>=nr (Only on NUMA kernels) 844 Number of pages allocated on memory node <node> 845 846> cat /proc/vmallocinfo 8470xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 848 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 8490xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 850 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 8510xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 852 phys=7fee8000 ioremap 8530xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 854 phys=7fee7000 ioremap 8550xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 8560xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 857 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 8580xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 859 pages=2 vmalloc N1=2 8600xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 861 /0x130 [x_tables] pages=4 vmalloc N0=4 8620xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 863 pages=14 vmalloc N2=14 8640xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 865 pages=4 vmalloc N1=4 8660xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 867 pages=2 vmalloc N1=2 8680xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 869 pages=10 vmalloc N0=10 870 871.............................................................................. 872 873softirqs: 874 875Provides counts of softirq handlers serviced since boot time, for each cpu. 876 877> cat /proc/softirqs 878 CPU0 CPU1 CPU2 CPU3 879 HI: 0 0 0 0 880 TIMER: 27166 27120 27097 27034 881 NET_TX: 0 0 0 17 882 NET_RX: 42 0 0 39 883 BLOCK: 0 0 107 1121 884 TASKLET: 0 0 0 290 885 SCHED: 27035 26983 26971 26746 886 HRTIMER: 0 0 0 0 887 RCU: 1678 1769 2178 2250 888 889 8901.3 IDE devices in /proc/ide 891---------------------------- 892 893The subdirectory /proc/ide contains information about all IDE devices of which 894the kernel is aware. There is one subdirectory for each IDE controller, the 895file drivers and a link for each IDE device, pointing to the device directory 896in the controller specific subtree. 897 898The file drivers contains general information about the drivers used for the 899IDE devices: 900 901 > cat /proc/ide/drivers 902 ide-cdrom version 4.53 903 ide-disk version 1.08 904 905More detailed information can be found in the controller specific 906subdirectories. These are named ide0, ide1 and so on. Each of these 907directories contains the files shown in table 1-6. 908 909 910Table 1-6: IDE controller info in /proc/ide/ide? 911.............................................................................. 912 File Content 913 channel IDE channel (0 or 1) 914 config Configuration (only for PCI/IDE bridge) 915 mate Mate name 916 model Type/Chipset of IDE controller 917.............................................................................. 918 919Each device connected to a controller has a separate subdirectory in the 920controllers directory. The files listed in table 1-7 are contained in these 921directories. 922 923 924Table 1-7: IDE device information 925.............................................................................. 926 File Content 927 cache The cache 928 capacity Capacity of the medium (in 512Byte blocks) 929 driver driver and version 930 geometry physical and logical geometry 931 identify device identify block 932 media media type 933 model device identifier 934 settings device setup 935 smart_thresholds IDE disk management thresholds 936 smart_values IDE disk management values 937.............................................................................. 938 939The most interesting file is settings. This file contains a nice overview of 940the drive parameters: 941 942 # cat /proc/ide/ide0/hda/settings 943 name value min max mode 944 ---- ----- --- --- ---- 945 bios_cyl 526 0 65535 rw 946 bios_head 255 0 255 rw 947 bios_sect 63 0 63 rw 948 breada_readahead 4 0 127 rw 949 bswap 0 0 1 r 950 file_readahead 72 0 2097151 rw 951 io_32bit 0 0 3 rw 952 keepsettings 0 0 1 rw 953 max_kb_per_request 122 1 127 rw 954 multcount 0 0 8 rw 955 nice1 1 0 1 rw 956 nowerr 0 0 1 rw 957 pio_mode write-only 0 255 w 958 slow 0 0 1 rw 959 unmaskirq 0 0 1 rw 960 using_dma 0 0 1 rw 961 962 9631.4 Networking info in /proc/net 964-------------------------------- 965 966The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 967additional values you get for IP version 6 if you configure the kernel to 968support this. Table 1-9 lists the files and their meaning. 969 970 971Table 1-8: IPv6 info in /proc/net 972.............................................................................. 973 File Content 974 udp6 UDP sockets (IPv6) 975 tcp6 TCP sockets (IPv6) 976 raw6 Raw device statistics (IPv6) 977 igmp6 IP multicast addresses, which this host joined (IPv6) 978 if_inet6 List of IPv6 interface addresses 979 ipv6_route Kernel routing table for IPv6 980 rt6_stats Global IPv6 routing tables statistics 981 sockstat6 Socket statistics (IPv6) 982 snmp6 Snmp data (IPv6) 983.............................................................................. 984 985 986Table 1-9: Network info in /proc/net 987.............................................................................. 988 File Content 989 arp Kernel ARP table 990 dev network devices with statistics 991 dev_mcast the Layer2 multicast groups a device is listening too 992 (interface index, label, number of references, number of bound 993 addresses). 994 dev_stat network device status 995 ip_fwchains Firewall chain linkage 996 ip_fwnames Firewall chain names 997 ip_masq Directory containing the masquerading tables 998 ip_masquerade Major masquerading table 999 netstat Network statistics 1000 raw raw device statistics
1001 route Kernel routing table 1002 rpc Directory containing rpc info 1003 rt_cache Routing cache 1004 snmp SNMP data 1005 sockstat Socket statistics 1006 tcp TCP sockets 1007 udp UDP sockets 1008 unix UNIX domain sockets 1009 wireless Wireless interface data (Wavelan etc) 1010 igmp IP multicast addresses, which this host joined 1011 psched Global packet scheduler parameters. 1012 netlink List of PF_NETLINK sockets 1013 ip_mr_vifs List of multicast virtual interfaces 1014 ip_mr_cache List of multicast routing cache 1015.............................................................................. 1016 1017You can use this information to see which network devices are available in 1018your system and how much traffic was routed over those devices: 1019 1020 > cat /proc/net/dev 1021 Inter-|Receive |[... 1022 face |bytes packets errs drop fifo frame compressed multicast|[... 1023 lo: 908188 5596 0 0 0 0 0 0 [... 1024 ppp0:15475140 20721 410 0 0 410 0 0 [... 1025 eth0: 614530 7085 0 0 0 0 0 1 [... 1026 1027 ...] Transmit 1028 ...] bytes packets errs drop fifo colls carrier compressed 1029 ...] 908188 5596 0 0 0 0 0 0 1030 ...] 1375103 17405 0 0 0 0 0 0 1031 ...] 1703981 5535 0 0 0 3 0 0 1032 1033In addition, each Channel Bond interface has its own directory. For 1034example, the bond0 device will have a directory called /proc/net/bond0/. 1035It will contain information that is specific to that bond, such as the 1036current slaves of the bond, the link status of the slaves, and how 1037many times the slaves link has failed. 1038 10391.5 SCSI info 1040------------- 1041 1042If you have a SCSI host adapter in your system, you'll find a subdirectory 1043named after the driver for this adapter in /proc/scsi. You'll also see a list 1044of all recognized SCSI devices in /proc/scsi: 1045 1046 >cat /proc/scsi/scsi 1047 Attached devices: 1048 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1049 Vendor: IBM Model: DGHS09U Rev: 03E0 1050 Type: Direct-Access ANSI SCSI revision: 03 1051 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1052 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1053 Type: CD-ROM ANSI SCSI revision: 02 1054 1055 1056The directory named after the driver has one file for each adapter found in 1057the system. These files contain information about the controller, including 1058the used IRQ and the IO address range. The amount of information shown is 1059dependent on the adapter you use. The example shows the output for an Adaptec 1060AHA-2940 SCSI adapter: 1061 1062 > cat /proc/scsi/aic7xxx/0 1063 1064 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1065 Compile Options: 1066 TCQ Enabled By Default : Disabled 1067 AIC7XXX_PROC_STATS : Disabled 1068 AIC7XXX_RESET_DELAY : 5 1069 Adapter Configuration: 1070 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1071 Ultra Wide Controller 1072 PCI MMAPed I/O Base: 0xeb001000 1073 Adapter SEEPROM Config: SEEPROM found and used. 1074 Adaptec SCSI BIOS: Enabled 1075 IRQ: 10 1076 SCBs: Active 0, Max Active 2, 1077 Allocated 15, HW 16, Page 255 1078 Interrupts: 160328 1079 BIOS Control Word: 0x18b6 1080 Adapter Control Word: 0x005b 1081 Extended Translation: Enabled 1082 Disconnect Enable Flags: 0xffff 1083 Ultra Enable Flags: 0x0001 1084 Tag Queue Enable Flags: 0x0000 1085 Ordered Queue Tag Flags: 0x0000 1086 Default Tag Queue Depth: 8 1087 Tagged Queue By Device array for aic7xxx host instance 0: 1088 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1089 Actual queue depth per device for aic7xxx host instance 0: 1090 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1091 Statistics: 1092 (scsi0:0:0:0) 1093 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1094 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1095 Total transfers 160151 (74577 reads and 85574 writes) 1096 (scsi0:0:6:0) 1097 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1098 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1099 Total transfers 0 (0 reads and 0 writes) 1100 1101 11021.6 Parallel port info in /proc/parport 1103--------------------------------------- 1104 1105The directory /proc/parport contains information about the parallel ports of 1106your system. It has one subdirectory for each port, named after the port 1107number (0,1,2,...). 1108 1109These directories contain the four files shown in Table 1-10. 1110 1111 1112Table 1-10: Files in /proc/parport 1113.............................................................................. 1114 File Content 1115 autoprobe Any IEEE-1284 device ID information that has been acquired. 1116 devices list of the device drivers using that port. A + will appear by the 1117 name of the device currently using the port (it might not appear 1118 against any). 1119 hardware Parallel port's base address, IRQ line and DMA channel. 1120 irq IRQ that parport is using for that port. This is in a separate 1121 file to allow you to alter it by writing a new value in (IRQ 1122 number or none). 1123.............................................................................. 1124 11251.7 TTY info in /proc/tty 1126------------------------- 1127 1128Information about the available and actually used tty's can be found in the 1129directory /proc/tty.You'll find entries for drivers and line disciplines in 1130this directory, as shown in Table 1-11. 1131 1132 1133Table 1-11: Files in /proc/tty 1134.............................................................................. 1135 File Content 1136 drivers list of drivers and their usage 1137 ldiscs registered line disciplines 1138 driver/serial usage statistic and status of single tty lines 1139.............................................................................. 1140 1141To see which tty's are currently in use, you can simply look into the file 1142/proc/tty/drivers: 1143 1144 > cat /proc/tty/drivers 1145 pty_slave /dev/pts 136 0-255 pty:slave 1146 pty_master /dev/ptm 128 0-255 pty:master 1147 pty_slave /dev/ttyp 3 0-255 pty:slave 1148 pty_master /dev/pty 2 0-255 pty:master 1149 serial /dev/cua 5 64-67 serial:callout 1150 serial /dev/ttyS 4 64-67 serial 1151 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1152 /dev/ptmx /dev/ptmx 5 2 system 1153 /dev/console /dev/console 5 1 system:console 1154 /dev/tty /dev/tty 5 0 system:/dev/tty 1155 unknown /dev/tty 4 1-63 console 1156 1157 11581.8 Miscellaneous kernel statistics in /proc/stat 1159------------------------------------------------- 1160 1161Various pieces of information about kernel activity are available in the 1162/proc/stat file. All of the numbers reported in this file are aggregates 1163since the system first booted. For a quick look, simply cat the file: 1164 1165 > cat /proc/stat 1166 cpu 2255 34 2290 22625563 6290 127 456 0 0 1167 cpu0 1132 34 1441 11311718 3675 127 438 0 0 1168 cpu1 1123 0 849 11313845 2614 0 18 0 0 1169 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1170 ctxt 1990473 1171 btime 1062191376 1172 processes 2915 1173 procs_running 1 1174 procs_blocked 0 1175 softirq 183433 0 21755 12 39 1137 231 21459 2263 1176 1177The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1178lines. These numbers identify the amount of time the CPU has spent performing 1179different kinds of work. Time units are in USER_HZ (typically hundredths of a 1180second). The meanings of the columns are as follows, from left to right: 1181 1182- user: normal processes executing in user mode 1183- nice: niced processes executing in user mode 1184- system: processes executing in kernel mode 1185- idle: twiddling thumbs 1186- iowait: waiting for I/O to complete 1187- irq: servicing interrupts 1188- softirq: servicing softirqs 1189- steal: involuntary wait 1190- guest: running a normal guest 1191- guest_nice: running a niced guest 1192 1193The "intr" line gives counts of interrupts serviced since boot time, for each 1194of the possible system interrupts. The first column is the total of all 1195interrupts serviced; each subsequent column is the total for that particular 1196interrupt. 1197 1198The "ctxt" line gives the total number of context switches across all CPUs. 1199 1200The "btime" line gives the time at which the system booted, in seconds since 1201the Unix epoch. 1202 1203The "processes" line gives the number of processes and threads created, which 1204includes (but is not limited to) those created by calls to the fork() and 1205clone() system calls. 1206 1207The "procs_running" line gives the total number of threads that are 1208running or ready to run (i.e., the total number of runnable threads). 1209 1210The "procs_blocked" line gives the number of processes currently blocked, 1211waiting for I/O to complete. 1212 1213The "softirq" line gives counts of softirqs serviced since boot time, for each 1214of the possible system softirqs. The first column is the total of all 1215softirqs serviced; each subsequent column is the total for that particular 1216softirq. 1217 1218 12191.9 Ext4 file system parameters 1220------------------------------ 1221 1222Information about mounted ext4 file systems can be found in 1223/proc/fs/ext4. Each mounted filesystem will have a directory in 1224/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1225/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1226in Table 1-12, below. 1227 1228Table 1-12: Files in /proc/fs/ext4/<devname> 1229.............................................................................. 1230 File Content 1231 mb_groups details of multiblock allocator buddy cache of free blocks 1232.............................................................................. 1233 12342.0 /proc/consoles 1235------------------ 1236Shows registered system console lines. 1237 1238To see which character device lines are currently used for the system console 1239/dev/console, you may simply look into the file /proc/consoles: 1240 1241 > cat /proc/consoles 1242 tty0 -WU (ECp) 4:7 1243 ttyS0 -W- (Ep) 4:64 1244 1245The columns are: 1246 1247 device name of the device 1248 operations R = can do read operations 1249 W = can do write operations 1250 U = can do unblank 1251 flags E = it is enabled 1252 C = it is preferred console 1253 B = it is primary boot console 1254 p = it is used for printk buffer 1255 b = it is not a TTY but a Braille device 1256 a = it is safe to use when cpu is offline 1257 major:minor major and minor number of the device separated by a colon 1258 1259------------------------------------------------------------------------------ 1260Summary 1261------------------------------------------------------------------------------ 1262The /proc file system serves information about the running system. It not only 1263allows access to process data but also allows you to request the kernel status 1264by reading files in the hierarchy. 1265 1266The directory structure of /proc reflects the types of information and makes 1267it easy, if not obvious, where to look for specific data. 1268------------------------------------------------------------------------------ 1269 1270------------------------------------------------------------------------------ 1271CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1272------------------------------------------------------------------------------ 1273 1274------------------------------------------------------------------------------ 1275In This Chapter 1276------------------------------------------------------------------------------ 1277* Modifying kernel parameters by writing into files found in /proc/sys 1278* Exploring the files which modify certain parameters 1279* Review of the /proc/sys file tree 1280------------------------------------------------------------------------------ 1281 1282 1283A very interesting part of /proc is the directory /proc/sys. This is not only 1284a source of information, it also allows you to change parameters within the 1285kernel. Be very careful when attempting this. You can optimize your system, 1286but you can also cause it to crash. Never alter kernel parameters on a 1287production system. Set up a development machine and test to make sure that 1288everything works the way you want it to. You may have no alternative but to 1289reboot the machine once an error has been made. 1290 1291To change a value, simply echo the new value into the file. An example is 1292given below in the section on the file system data. You need to be root to do 1293this. You can create your own boot script to perform this every time your 1294system boots. 1295 1296The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1297general things in the operation of the Linux kernel. Since some of the files 1298can inadvertently disrupt your system, it is advisable to read both 1299documentation and source before actually making adjustments. In any case, be 1300very careful when writing to any of these files. The entries in /proc may 1301change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1302review the kernel documentation in the directory /usr/src/linux/Documentation. 1303This chapter is heavily based on the documentation included in the pre 2.2 1304kernels, and became part of it in version 2.2.1 of the Linux kernel. 1305 1306Please see: Documentation/sysctl/ directory for descriptions of these 1307entries. 1308 1309------------------------------------------------------------------------------ 1310Summary 1311------------------------------------------------------------------------------ 1312Certain aspects of kernel behavior can be modified at runtime, without the 1313need to recompile the kernel, or even to reboot the system. The files in the 1314/proc/sys tree can not only be read, but also modified. You can use the echo 1315command to write value into these files, thereby changing the default settings 1316of the kernel. 1317------------------------------------------------------------------------------ 1318 1319------------------------------------------------------------------------------ 1320CHAPTER 3: PER-PROCESS PARAMETERS 1321------------------------------------------------------------------------------ 1322 13233.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1324-------------------------------------------------------------------------------- 1325 1326These file can be used to adjust the badness heuristic used to select which 1327process gets killed in out of memory conditions. 1328 1329The badness heuristic assigns a value to each candidate task ranging from 0 1330(never kill) to 1000 (always kill) to determine which process is targeted. The 1331units are roughly a proportion along that range of allowed memory the process 1332may allocate from based on an estimation of its current memory and swap use. 1333For example, if a task is using all allowed memory, its badness score will be 13341000. If it is using half of its allowed memory, its score will be 500. 1335 1336There is an additional factor included in the badness score: root 1337processes are given 3% extra memory over other tasks. 1338 1339The amount of "allowed" memory depends on the context in which the oom killer 1340was called. If it is due to the memory assigned to the allocating task's cpuset 1341being exhausted, the allowed memory represents the set of mems assigned to that 1342cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1343memory represents the set of mempolicy nodes. If it is due to a memory 1344limit (or swap limit) being reached, the allowed memory is that configured 1345limit. Finally, if it is due to the entire system being out of memory, the 1346allowed memory represents all allocatable resources. 1347 1348The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1349is used to determine which task to kill. Acceptable values range from -1000 1350(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1351polarize the preference for oom killing either by always preferring a certain 1352task or completely disabling it. The lowest possible value, -1000, is 1353equivalent to disabling oom killing entirely for that task since it will always 1354report a badness score of 0. 1355 1356Consequently, it is very simple for userspace to define the amount of memory to 1357consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1358example, is roughly equivalent to allowing the remainder of tasks sharing the 1359same system, cpuset, mempolicy, or memory controller resources to use at least 136050% more memory. A value of -500, on the other hand, would be roughly 1361equivalent to discounting 50% of the task's allowed memory from being considered 1362as scoring against the task. 1363 1364For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1365be used to tune the badness score. Its acceptable values range from -16 1366(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1367(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1368scaled linearly with /proc/<pid>/oom_score_adj. 1369 1370The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1371value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1372requires CAP_SYS_RESOURCE. 1373 1374Caveat: when a parent task is selected, the oom killer will sacrifice any first 1375generation children with separate address spaces instead, if possible. This 1376avoids servers and important system daemons from being killed and loses the 1377minimal amount of work. 1378 1379 13803.2 /proc/<pid>/oom_score - Display current oom-killer score 1381------------------------------------------------------------- 1382 1383This file can be used to check the current score used by the oom-killer is for 1384any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1385process should be killed in an out-of-memory situation. 1386 1387 13883.3 /proc/<pid>/io - Display the IO accounting fields 1389------------------------------------------------------- 1390 1391This file contains IO statistics for each running process 1392 1393Example 1394------- 1395 1396test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1397[1] 3828 1398 1399test:/tmp # cat /proc/3828/io 1400rchar: 323934931 1401wchar: 323929600 1402syscr: 632687 1403syscw: 632675 1404read_bytes: 0 1405write_bytes: 323932160 1406cancelled_write_bytes: 0 1407 1408 1409Description 1410----------- 1411 1412rchar 1413----- 1414 1415I/O counter: chars read 1416The number of bytes which this task has caused to be read from storage. This 1417is simply the sum of bytes which this process passed to read() and pread(). 1418It includes things like tty IO and it is unaffected by whether or not actual 1419physical disk IO was required (the read might have been satisfied from 1420pagecache) 1421 1422 1423wchar 1424----- 1425 1426I/O counter: chars written 1427The number of bytes which this task has caused, or shall cause to be written 1428to disk. Similar caveats apply here as with rchar. 1429 1430 1431syscr 1432----- 1433 1434I/O counter: read syscalls 1435Attempt to count the number of read I/O operations, i.e. syscalls like read() 1436and pread(). 1437 1438 1439syscw 1440----- 1441 1442I/O counter: write syscalls 1443Attempt to count the number of write I/O operations, i.e. syscalls like 1444write() and pwrite(). 1445 1446 1447read_bytes 1448---------- 1449 1450I/O counter: bytes read 1451Attempt to count the number of bytes which this process really did cause to 1452be fetched from the storage layer. Done at the submit_bio() level, so it is 1453accurate for block-backed filesystems. <please add status regarding NFS and 1454CIFS at a later time> 1455 1456 1457write_bytes 1458----------- 1459 1460I/O counter: bytes written 1461Attempt to count the number of bytes which this process caused to be sent to 1462the storage layer. This is done at page-dirtying time. 1463 1464 1465cancelled_write_bytes 1466--------------------- 1467 1468The big inaccuracy here is truncate. If a process writes 1MB to a file and 1469then deletes the file, it will in fact perform no writeout. But it will have 1470been accounted as having caused 1MB of write. 1471In other words: The number of bytes which this process caused to not happen, 1472by truncating pagecache. A task can cause "negative" IO too. If this task 1473truncates some dirty pagecache, some IO which another task has been accounted 1474for (in its write_bytes) will not be happening. We _could_ just subtract that 1475from the truncating task's write_bytes, but there is information loss in doing 1476that. 1477 1478 1479Note 1480---- 1481 1482At its current implementation state, this is a bit racy on 32-bit machines: if 1483process A reads process B's /proc/pid/io while process B is updating one of 1484those 64-bit counters, process A could see an intermediate result. 1485 1486 1487More information about this can be found within the taskstats documentation in 1488Documentation/accounting. 1489 14903.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1491--------------------------------------------------------------- 1492When a process is dumped, all anonymous memory is written to a core file as 1493long as the size of the core file isn't limited. But sometimes we don't want 1494to dump some memory segments, for example, huge shared memory. Conversely, 1495sometimes we want to save file-backed memory segments into a core file, not 1496only the individual files. 1497 1498/proc/<pid>/coredump_filter allows you to customize which memory segments 1499will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1500of memory types. If a bit of the bitmask is set, memory segments of the 1501corresponding memory type are dumped, otherwise they are not dumped. 1502 1503The following 7 memory types are supported: 1504 - (bit 0) anonymous private memory 1505 - (bit 1) anonymous shared memory 1506 - (bit 2) file-backed private memory 1507 - (bit 3) file-backed shared memory 1508 - (bit 4) ELF header pages in file-backed private memory areas (it is 1509 effective only if the bit 2 is cleared) 1510 - (bit 5) hugetlb private memory 1511 - (bit 6) hugetlb shared memory 1512 1513 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1514 are always dumped regardless of the bitmask status. 1515 1516 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only 1517 effected by bit 5-6. 1518 1519Default value of coredump_filter is 0x23; this means all anonymous memory 1520segments and hugetlb private memory are dumped. 1521 1522If you don't want to dump all shared memory segments attached to pid 1234, 1523write 0x21 to the process's proc file. 1524 1525 $ echo 0x21 > /proc/1234/coredump_filter 1526 1527When a new process is created, the process inherits the bitmask status from its 1528parent. It is useful to set up coredump_filter before the program runs. 1529For example: 1530 1531 $ echo 0x7 > /proc/self/coredump_filter 1532 $ ./some_program 1533 15343.5 /proc/<pid>/mountinfo - Information about mounts 1535-------------------------------------------------------- 1536 1537This file contains lines of the form: 1538 153936 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1540(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1541 1542(1) mount ID: unique identifier of the mount (may be reused after umount) 1543(2) parent ID: ID of parent (or of self for the top of the mount tree) 1544(3) major:minor: value of st_dev for files on filesystem 1545(4) root: root of the mount within the filesystem 1546(5) mount point: mount point relative to the process's root 1547(6) mount options: per mount options 1548(7) optional fields: zero or more fields of the form "tag[:value]" 1549(8) separator: marks the end of the optional fields 1550(9) filesystem type: name of filesystem of the form "type[.subtype]" 1551(10) mount source: filesystem specific information or "none" 1552(11) super options: per super block options 1553 1554Parsers should ignore all unrecognised optional fields. Currently the 1555possible optional fields are: 1556 1557shared:X mount is shared in peer group X 1558master:X mount is slave to peer group X 1559propagate_from:X mount is slave and receives propagation from peer group X (*) 1560unbindable mount is unbindable 1561 1562(*) X is the closest dominant peer group under the process's root. If 1563X is the immediate master of the mount, or if there's no dominant peer 1564group under the same root, then only the "master:X" field is present 1565and not the "propagate_from:X" field. 1566 1567For more information on mount propagation see: 1568 1569 Documentation/filesystems/sharedsubtree.txt 1570 1571 15723.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1573-------------------------------------------------------- 1574These files provide a method to access a tasks comm value. It also allows for 1575a task to set its own or one of its thread siblings comm value. The comm value 1576is limited in size compared to the cmdline value, so writing anything longer 1577then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1578comm value. 1579 1580 15813.7 /proc/<pid>/task/<tid>/children - Information about task children 1582------------------------------------------------------------------------- 1583This file provides a fast way to retrieve first level children pids 1584of a task pointed by <pid>/<tid> pair. The format is a space separated 1585stream of pids. 1586 1587Note the "first level" here -- if a child has own children they will 1588not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children 1589to obtain the descendants. 1590 1591Since this interface is intended to be fast and cheap it doesn't 1592guarantee to provide precise results and some children might be 1593skipped, especially if they've exited right after we printed their 1594pids, so one need to either stop or freeze processes being inspected 1595if precise results are needed. 1596 1597 1598------------------------------------------------------------------------------ 1599Configuring procfs 1600------------------------------------------------------------------------------ 1601 16024.1 Mount options 1603--------------------- 1604 1605The following mount options are supported: 1606 1607 hidepid= Set /proc/<pid>/ access mode. 1608 gid= Set the group authorized to learn processes information. 1609 1610hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories 1611(default). 1612 1613hidepid=1 means users may not access any /proc/<pid>/ directories but their 1614own. Sensitive files like cmdline, sched*, status are now protected against 1615other users. This makes it impossible to learn whether any user runs 1616specific program (given the program doesn't reveal itself by its behaviour). 1617As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, 1618poorly written programs passing sensitive information via program arguments are 1619now protected against local eavesdroppers. 1620 1621hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other 1622users. It doesn't mean that it hides a fact whether a process with a specific 1623pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), 1624but it hides process' uid and gid, which may be learned by stat()'ing 1625/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering 1626information about running processes, whether some daemon runs with elevated 1627privileges, whether other user runs some sensitive program, whether other users 1628run any program at all, etc. 1629 1630gid= defines a group authorized to learn processes information otherwise 1631prohibited by hidepid=. If you use some daemon like identd which needs to learn 1632information about processes information, just add identd to this group. 1633