1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config HAVE_IRQ_WORK 24 bool 25 26config IRQ_WORK 27 bool 28 depends on HAVE_IRQ_WORK 29 30config BUILDTIME_EXTABLE_SORT 31 bool 32 33menu "General setup" 34 35config EXPERIMENTAL 36 bool "Prompt for development and/or incomplete code/drivers" 37 ---help--- 38 Some of the various things that Linux supports (such as network 39 drivers, file systems, network protocols, etc.) can be in a state 40 of development where the functionality, stability, or the level of 41 testing is not yet high enough for general use. This is usually 42 known as the "alpha-test" phase among developers. If a feature is 43 currently in alpha-test, then the developers usually discourage 44 uninformed widespread use of this feature by the general public to 45 avoid "Why doesn't this work?" type mail messages. However, active 46 testing and use of these systems is welcomed. Just be aware that it 47 may not meet the normal level of reliability or it may fail to work 48 in some special cases. Detailed bug reports from people familiar 49 with the kernel internals are usually welcomed by the developers 50 (before submitting bug reports, please read the documents 51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 52 <file:Documentation/BUG-HUNTING>, and 53 <file:Documentation/oops-tracing.txt> in the kernel source). 54 55 This option will also make obsoleted drivers available. These are 56 drivers that have been replaced by something else, and/or are 57 scheduled to be removed in a future kernel release. 58 59 Unless you intend to help test and develop a feature or driver that 60 falls into this category, or you have a situation that requires 61 using these features, you should probably say N here, which will 62 cause the configurator to present you with fewer choices. If 63 you say Y here, you will be offered the choice of using features or 64 drivers that are currently considered to be in the alpha-test phase. 65 66config BROKEN 67 bool 68 69config BROKEN_ON_SMP 70 bool 71 depends on BROKEN || !SMP 72 default y 73 74config INIT_ENV_ARG_LIMIT 75 int 76 default 32 if !UML 77 default 128 if UML 78 help 79 Maximum of each of the number of arguments and environment 80 variables passed to init from the kernel command line. 81 82 83config CROSS_COMPILE 84 string "Cross-compiler tool prefix" 85 help 86 Same as running 'make CROSS_COMPILE=prefix-' but stored for 87 default make runs in this kernel build directory. You don't 88 need to set this unless you want the configured kernel build 89 directory to select the cross-compiler automatically. 90 91config LOCALVERSION 92 string "Local version - append to kernel release" 93 help 94 Append an extra string to the end of your kernel version. 95 This will show up when you type uname, for example. 96 The string you set here will be appended after the contents of 97 any files with a filename matching localversion* in your 98 object and source tree, in that order. Your total string can 99 be a maximum of 64 characters. 100 101config LOCALVERSION_AUTO 102 bool "Automatically append version information to the version string" 103 default y 104 help 105 This will try to automatically determine if the current tree is a 106 release tree by looking for git tags that belong to the current 107 top of tree revision. 108 109 A string of the format -gxxxxxxxx will be added to the localversion 110 if a git-based tree is found. The string generated by this will be 111 appended after any matching localversion* files, and after the value 112 set in CONFIG_LOCALVERSION. 113 114 (The actual string used here is the first eight characters produced 115 by running the command: 116 117 $ git rev-parse --verify HEAD 118 119 which is done within the script "scripts/setlocalversion".) 120 121config HAVE_KERNEL_GZIP 122 bool 123 124config HAVE_KERNEL_BZIP2 125 bool 126 127config HAVE_KERNEL_LZMA 128 bool 129 130config HAVE_KERNEL_XZ 131 bool 132 133config HAVE_KERNEL_LZO 134 bool 135 136choice 137 prompt "Kernel compression mode" 138 default KERNEL_GZIP 139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 140 help 141 The linux kernel is a kind of self-extracting executable. 142 Several compression algorithms are available, which differ 143 in efficiency, compression and decompression speed. 144 Compression speed is only relevant when building a kernel. 145 Decompression speed is relevant at each boot. 146 147 If you have any problems with bzip2 or lzma compressed 148 kernels, mail me (Alain Knaff) <email@example.com>. (An older 149 version of this functionality (bzip2 only), for 2.4, was 150 supplied by Christian Ludwig) 151 152 High compression options are mostly useful for users, who 153 are low on disk space (embedded systems), but for whom ram 154 size matters less. 155 156 If in doubt, select 'gzip' 157 158config KERNEL_GZIP 159 bool "Gzip" 160 depends on HAVE_KERNEL_GZIP 161 help 162 The old and tried gzip compression. It provides a good balance 163 between compression ratio and decompression speed. 164 165config KERNEL_BZIP2 166 bool "Bzip2" 167 depends on HAVE_KERNEL_BZIP2 168 help 169 Its compression ratio and speed is intermediate. 170 Decompression speed is slowest among the choices. The kernel 171 size is about 10% smaller with bzip2, in comparison to gzip. 172 Bzip2 uses a large amount of memory. For modern kernels you 173 will need at least 8MB RAM or more for booting. 174 175config KERNEL_LZMA 176 bool "LZMA" 177 depends on HAVE_KERNEL_LZMA 178 help 179 This compression algorithm's ratio is best. Decompression speed 180 is between gzip and bzip2. Compression is slowest. 181 The kernel size is about 33% smaller with LZMA in comparison to gzip. 182 183config KERNEL_XZ 184 bool "XZ" 185 depends on HAVE_KERNEL_XZ 186 help 187 XZ uses the LZMA2 algorithm and instruction set specific 188 BCJ filters which can improve compression ratio of executable 189 code. The size of the kernel is about 30% smaller with XZ in 190 comparison to gzip. On architectures for which there is a BCJ 191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 192 will create a few percent smaller kernel than plain LZMA. 193 194 The speed is about the same as with LZMA: The decompression 195 speed of XZ is better than that of bzip2 but worse than gzip 196 and LZO. Compression is slow. 197 198config KERNEL_LZO 199 bool "LZO" 200 depends on HAVE_KERNEL_LZO 201 help 202 Its compression ratio is the poorest among the choices. The kernel 203 size is about 10% bigger than gzip; however its speed 204 (both compression and decompression) is the fastest. 205 206endchoice 207 208config DEFAULT_HOSTNAME 209 string "Default hostname" 210 default "(none)" 211 help 212 This option determines the default system hostname before userspace 213 calls sethostname(2). The kernel traditionally uses "(none)" here, 214 but you may wish to use a different default here to make a minimal 215 system more usable with less configuration. 216 217config SWAP 218 bool "Support for paging of anonymous memory (swap)" 219 depends on MMU && BLOCK 220 default y 221 help 222 This option allows you to choose whether you want to have support 223 for so called swap devices or swap files in your kernel that are 224 used to provide more virtual memory than the actual RAM present 225 in your computer. If unsure say Y. 226 227config SYSVIPC 228 bool "System V IPC" 229 ---help--- 230 Inter Process Communication is a suite of library functions and 231 system calls which let processes (running programs) synchronize and 232 exchange information. It is generally considered to be a good thing, 233 and some programs won't run unless you say Y here. In particular, if 234 you want to run the DOS emulator dosemu under Linux (read the 235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 236 you'll need to say Y here. 237 238 You can find documentation about IPC with "info ipc" and also in 239 section 6.4 of the Linux Programmer's Guide, available from 240 <http://www.tldp.org/guides.html>. 241 242config SYSVIPC_SYSCTL 243 bool 244 depends on SYSVIPC 245 depends on SYSCTL 246 default y 247 248config POSIX_MQUEUE 249 bool "POSIX Message Queues" 250 depends on NET && EXPERIMENTAL 251 ---help--- 252 POSIX variant of message queues is a part of IPC. In POSIX message 253 queues every message has a priority which decides about succession 254 of receiving it by a process. If you want to compile and run 255 programs written e.g. for Solaris with use of its POSIX message 256 queues (functions mq_*) say Y here. 257 258 POSIX message queues are visible as a filesystem called 'mqueue' 259 and can be mounted somewhere if you want to do filesystem 260 operations on message queues. 261 262 If unsure, say Y. 263 264config POSIX_MQUEUE_SYSCTL 265 bool 266 depends on POSIX_MQUEUE 267 depends on SYSCTL 268 default y 269 270config FHANDLE 271 bool "open by fhandle syscalls" 272 select EXPORTFS 273 help 274 If you say Y here, a user level program will be able to map 275 file names to handle and then later use the handle for 276 different file system operations. This is useful in implementing 277 userspace file servers, which now track files using handles instead 278 of names. The handle would remain the same even if file names 279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 280 syscalls. 281 282config AUDIT 283 bool "Auditing support" 284 depends on NET 285 help 286 Enable auditing infrastructure that can be used with another 287 kernel subsystem, such as SELinux (which requires this for 288 logging of avc messages output). Does not do system-call 289 auditing without CONFIG_AUDITSYSCALL. 290 291config AUDITSYSCALL 292 bool "Enable system-call auditing support" 293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT)) 294 default y if SECURITY_SELINUX 295 help 296 Enable low-overhead system-call auditing infrastructure that 297 can be used independently or with another kernel subsystem, 298 such as SELinux. 299 300config AUDIT_WATCH 301 def_bool y 302 depends on AUDITSYSCALL 303 select FSNOTIFY 304 305config AUDIT_TREE 306 def_bool y 307 depends on AUDITSYSCALL 308 select FSNOTIFY 309 310config AUDIT_LOGINUID_IMMUTABLE 311 bool "Make audit loginuid immutable" 312 depends on AUDIT 313 help 314 The config option toggles if a task setting its loginuid requires 315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions 316 but should instead only allow setting its loginuid if it was never 317 previously set. On systems which use systemd or a similar central 318 process to restart login services this should be set to true. On older 319 systems in which an admin would typically have to directly stop and 320 start processes this should be set to false. Setting this to true allows 321 one to drop potentially dangerous capabilites from the login tasks, 322 but may not be backwards compatible with older init systems. 323 324source "kernel/irq/Kconfig" 325source "kernel/time/Kconfig" 326 327menu "CPU/Task time and stats accounting" 328 329choice 330 prompt "Cputime accounting" 331 default TICK_CPU_ACCOUNTING if !PPC64 332 default VIRT_CPU_ACCOUNTING if PPC64 333 334# Kind of a stub config for the pure tick based cputime accounting 335config TICK_CPU_ACCOUNTING 336 bool "Simple tick based cputime accounting" 337 depends on !S390 338 help 339 This is the basic tick based cputime accounting that maintains 340 statistics about user, system and idle time spent on per jiffies 341 granularity. 342 343 If unsure, say Y. 344 345config VIRT_CPU_ACCOUNTING 346 bool "Deterministic task and CPU time accounting" 347 depends on HAVE_VIRT_CPU_ACCOUNTING 348 help 349 Select this option to enable more accurate task and CPU time 350 accounting. This is done by reading a CPU counter on each 351 kernel entry and exit and on transitions within the kernel 352 between system, softirq and hardirq state, so there is a 353 small performance impact. In the case of s390 or IBM POWER > 5, 354 this also enables accounting of stolen time on logically-partitioned 355 systems. 356 357config IRQ_TIME_ACCOUNTING 358 bool "Fine granularity task level IRQ time accounting" 359 depends on HAVE_IRQ_TIME_ACCOUNTING 360 help 361 Select this option to enable fine granularity task irq time 362 accounting. This is done by reading a timestamp on each 363 transitions between softirq and hardirq state, so there can be a 364 small performance impact. 365 366 If in doubt, say N here. 367 368endchoice 369 370config BSD_PROCESS_ACCT 371 bool "BSD Process Accounting" 372 help 373 If you say Y here, a user level program will be able to instruct the 374 kernel (via a special system call) to write process accounting 375 information to a file: whenever a process exits, information about 376 that process will be appended to the file by the kernel. The 377 information includes things such as creation time, owning user, 378 command name, memory usage, controlling terminal etc. (the complete 379 list is in the struct acct in <file:include/linux/acct.h>). It is 380 up to the user level program to do useful things with this 381 information. This is generally a good idea, so say Y. 382 383config BSD_PROCESS_ACCT_V3 384 bool "BSD Process Accounting version 3 file format" 385 depends on BSD_PROCESS_ACCT 386 default n 387 help 388 If you say Y here, the process accounting information is written 389 in a new file format that also logs the process IDs of each 390 process and it's parent. Note that this file format is incompatible 391 with previous v0/v1/v2 file formats, so you will need updated tools 392 for processing it. A preliminary version of these tools is available 393 at <http://www.gnu.org/software/acct/>. 394 395config TASKSTATS 396 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 397 depends on NET 398 default n 399 help 400 Export selected statistics for tasks/processes through the 401 generic netlink interface. Unlike BSD process accounting, the 402 statistics are available during the lifetime of tasks/processes as 403 responses to commands. Like BSD accounting, they are sent to user 404 space on task exit. 405 406 Say N if unsure. 407 408config TASK_DELAY_ACCT 409 bool "Enable per-task delay accounting (EXPERIMENTAL)" 410 depends on TASKSTATS 411 help 412 Collect information on time spent by a task waiting for system 413 resources like cpu, synchronous block I/O completion and swapping 414 in pages. Such statistics can help in setting a task's priorities 415 relative to other tasks for cpu, io, rss limits etc. 416 417 Say N if unsure. 418 419config TASK_XACCT 420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 421 depends on TASKSTATS 422 help 423 Collect extended task accounting data and send the data 424 to userland for processing over the taskstats interface. 425 426 Say N if unsure. 427 428config TASK_IO_ACCOUNTING 429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 430 depends on TASK_XACCT 431 help 432 Collect information on the number of bytes of storage I/O which this 433 task has caused. 434 435 Say N if unsure. 436 437endmenu # "CPU/Task time and stats accounting" 438 439menu "RCU Subsystem" 440 441choice 442 prompt "RCU Implementation" 443 default TREE_RCU 444 445config TREE_RCU 446 bool "Tree-based hierarchical RCU" 447 depends on !PREEMPT && SMP 448 help 449 This option selects the RCU implementation that is 450 designed for very large SMP system with hundreds or 451 thousands of CPUs. It also scales down nicely to 452 smaller systems. 453 454config TREE_PREEMPT_RCU 455 bool "Preemptible tree-based hierarchical RCU" 456 depends on PREEMPT && SMP 457 help 458 This option selects the RCU implementation that is 459 designed for very large SMP systems with hundreds or 460 thousands of CPUs, but for which real-time response 461 is also required. It also scales down nicely to 462 smaller systems. 463 464config TINY_RCU 465 bool "UP-only small-memory-footprint RCU" 466 depends on !PREEMPT && !SMP 467 help 468 This option selects the RCU implementation that is 469 designed for UP systems from which real-time response 470 is not required. This option greatly reduces the 471 memory footprint of RCU. 472 473config TINY_PREEMPT_RCU 474 bool "Preemptible UP-only small-memory-footprint RCU" 475 depends on PREEMPT && !SMP 476 help 477 This option selects the RCU implementation that is designed 478 for real-time UP systems. This option greatly reduces the 479 memory footprint of RCU. 480 481endchoice 482 483config PREEMPT_RCU 484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 485 help 486 This option enables preemptible-RCU code that is common between 487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 488 489config CONTEXT_TRACKING 490 bool 491 492config RCU_USER_QS 493 bool "Consider userspace as in RCU extended quiescent state" 494 depends on HAVE_CONTEXT_TRACKING && SMP 495 select CONTEXT_TRACKING 496 help 497 This option sets hooks on kernel / userspace boundaries and 498 puts RCU in extended quiescent state when the CPU runs in 499 userspace. It means that when a CPU runs in userspace, it is 500 excluded from the global RCU state machine and thus doesn't 501 try to keep the timer tick on for RCU. 502 503 Unless you want to hack and help the development of the full 504 dynticks mode, you shouldn't enable this option. It also 505 adds unnecessary overhead. 506 507 If unsure say N 508 509config CONTEXT_TRACKING_FORCE 510 bool "Force context tracking" 511 depends on CONTEXT_TRACKING 512 help 513 Probe on user/kernel boundaries by default in order to 514 test the features that rely on it such as userspace RCU extended 515 quiescent states. 516 This test is there for debugging until we have a real user like the 517 full dynticks mode. 518 519config RCU_FANOUT 520 int "Tree-based hierarchical RCU fanout value" 521 range 2 64 if 64BIT 522 range 2 32 if !64BIT 523 depends on TREE_RCU || TREE_PREEMPT_RCU 524 default 64 if 64BIT 525 default 32 if !64BIT 526 help 527 This option controls the fanout of hierarchical implementations 528 of RCU, allowing RCU to work efficiently on machines with 529 large numbers of CPUs. This value must be at least the fourth 530 root of NR_CPUS, which allows NR_CPUS to be insanely large. 531 The default value of RCU_FANOUT should be used for production 532 systems, but if you are stress-testing the RCU implementation 533 itself, small RCU_FANOUT values allow you to test large-system 534 code paths on small(er) systems. 535 536 Select a specific number if testing RCU itself. 537 Take the default if unsure. 538 539config RCU_FANOUT_LEAF 540 int "Tree-based hierarchical RCU leaf-level fanout value" 541 range 2 RCU_FANOUT if 64BIT 542 range 2 RCU_FANOUT if !64BIT 543 depends on TREE_RCU || TREE_PREEMPT_RCU 544 default 16 545 help 546 This option controls the leaf-level fanout of hierarchical 547 implementations of RCU, and allows trading off cache misses 548 against lock contention. Systems that synchronize their 549 scheduling-clock interrupts for energy-efficiency reasons will 550 want the default because the smaller leaf-level fanout keeps 551 lock contention levels acceptably low. Very large systems 552 (hundreds or thousands of CPUs) will instead want to set this 553 value to the maximum value possible in order to reduce the 554 number of cache misses incurred during RCU's grace-period 555 initialization. These systems tend to run CPU-bound, and thus 556 are not helped by synchronized interrupts, and thus tend to 557 skew them, which reduces lock contention enough that large 558 leaf-level fanouts work well. 559 560 Select a specific number if testing RCU itself. 561 562 Select the maximum permissible value for large systems. 563 564 Take the default if unsure. 565 566config RCU_FANOUT_EXACT 567 bool "Disable tree-based hierarchical RCU auto-balancing" 568 depends on TREE_RCU || TREE_PREEMPT_RCU 569 default n 570 help 571 This option forces use of the exact RCU_FANOUT value specified, 572 regardless of imbalances in the hierarchy. This is useful for 573 testing RCU itself, and might one day be useful on systems with 574 strong NUMA behavior. 575 576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 577 578 Say N if unsure. 579 580config RCU_FAST_NO_HZ 581 bool "Accelerate last non-dyntick-idle CPU's grace periods" 582 depends on NO_HZ && SMP 583 default n 584 help 585 This option causes RCU to attempt to accelerate grace periods in 586 order to allow CPUs to enter dynticks-idle state more quickly. 587 On the other hand, this option increases the overhead of the 588 dynticks-idle checking, thus degrading scheduling latency. 589 590 Say Y if energy efficiency is critically important, and you don't 591 care about real-time response. 592 593 Say N if you are unsure. 594 595config TREE_RCU_TRACE 596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 597 select DEBUG_FS 598 help 599 This option provides tracing for the TREE_RCU and 600 TREE_PREEMPT_RCU implementations, permitting Makefile to 601 trivially select kernel/rcutree_trace.c. 602 603config RCU_BOOST 604 bool "Enable RCU priority boosting" 605 depends on RT_MUTEXES && PREEMPT_RCU 606 default n 607 help 608 This option boosts the priority of preempted RCU readers that 609 block the current preemptible RCU grace period for too long. 610 This option also prevents heavy loads from blocking RCU 611 callback invocation for all flavors of RCU. 612 613 Say Y here if you are working with real-time apps or heavy loads 614 Say N here if you are unsure. 615 616config RCU_BOOST_PRIO 617 int "Real-time priority to boost RCU readers to" 618 range 1 99 619 depends on RCU_BOOST 620 default 1 621 help 622 This option specifies the real-time priority to which long-term 623 preempted RCU readers are to be boosted. If you are working 624 with a real-time application that has one or more CPU-bound 625 threads running at a real-time priority level, you should set 626 RCU_BOOST_PRIO to a priority higher then the highest-priority 627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value 628 of 1 is appropriate in the common case, which is real-time 629 applications that do not have any CPU-bound threads. 630 631 Some real-time applications might not have a single real-time 632 thread that saturates a given CPU, but instead might have 633 multiple real-time threads that, taken together, fully utilize 634 that CPU. In this case, you should set RCU_BOOST_PRIO to 635 a priority higher than the lowest-priority thread that is 636 conspiring to prevent the CPU from running any non-real-time 637 tasks. For example, if one thread at priority 10 and another 638 thread at priority 5 are between themselves fully consuming 639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be 640 set to priority 6 or higher. 641 642 Specify the real-time priority, or take the default if unsure. 643 644config RCU_BOOST_DELAY 645 int "Milliseconds to delay boosting after RCU grace-period start" 646 range 0 3000 647 depends on RCU_BOOST 648 default 500 649 help 650 This option specifies the time to wait after the beginning of 651 a given grace period before priority-boosting preempted RCU 652 readers blocking that grace period. Note that any RCU reader 653 blocking an expedited RCU grace period is boosted immediately. 654 655 Accept the default if unsure. 656 657config RCU_NOCB_CPU 658 bool "Offload RCU callback processing from boot-selected CPUs" 659 depends on TREE_RCU || TREE_PREEMPT_RCU 660 default n 661 help 662 Use this option to reduce OS jitter for aggressive HPC or 663 real-time workloads. It can also be used to offload RCU 664 callback invocation to energy-efficient CPUs in battery-powered 665 asymmetric multiprocessors. 666 667 This option offloads callback invocation from the set of 668 CPUs specified at boot time by the rcu_nocbs parameter. 669 For each such CPU, a kthread ("rcuoN") will be created to 670 invoke callbacks, where the "N" is the CPU being offloaded. 671 Nothing prevents this kthread from running on the specified 672 CPUs, but (1) the kthreads may be preempted between each 673 callback, and (2) affinity or cgroups can be used to force 674 the kthreads to run on whatever set of CPUs is desired. 675 676 Say Y here if you want reduced OS jitter on selected CPUs. 677 Say N here if you are unsure. 678 679endmenu # "RCU Subsystem" 680 681config IKCONFIG 682 tristate "Kernel .config support" 683 ---help--- 684 This option enables the complete Linux kernel ".config" file 685 contents to be saved in the kernel. It provides documentation 686 of which kernel options are used in a running kernel or in an 687 on-disk kernel. This information can be extracted from the kernel 688 image file with the script scripts/extract-ikconfig and used as 689 input to rebuild the current kernel or to build another kernel. 690 It can also be extracted from a running kernel by reading 691 /proc/config.gz if enabled (below). 692 693config IKCONFIG_PROC 694 bool "Enable access to .config through /proc/config.gz" 695 depends on IKCONFIG && PROC_FS 696 ---help--- 697 This option enables access to the kernel configuration file 698 through /proc/config.gz. 699 700config LOG_BUF_SHIFT 701 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 702 range 12 21 703 default 17 704 help 705 Select kernel log buffer size as a power of 2. 706 Examples: 707 17 => 128 KB 708 16 => 64 KB 709 15 => 32 KB 710 14 => 16 KB 711 13 => 8 KB 712 12 => 4 KB 713 714# 715# Architectures with an unreliable sched_clock() should select this: 716# 717config HAVE_UNSTABLE_SCHED_CLOCK 718 bool 719 720# 721# For architectures that want to enable the support for NUMA-affine scheduler 722# balancing logic: 723# 724config ARCH_SUPPORTS_NUMA_BALANCING 725 bool 726 727# For architectures that (ab)use NUMA to represent different memory regions 728# all cpu-local but of different latencies, such as SuperH. 729# 730config ARCH_WANT_NUMA_VARIABLE_LOCALITY 731 bool 732 733# 734# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE 735config ARCH_WANTS_PROT_NUMA_PROT_NONE 736 bool 737 738config ARCH_USES_NUMA_PROT_NONE 739 bool 740 default y 741 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE 742 depends on NUMA_BALANCING 743 744config NUMA_BALANCING_DEFAULT_ENABLED 745 bool "Automatically enable NUMA aware memory/task placement" 746 default y 747 depends on NUMA_BALANCING 748 help 749 If set, autonumic NUMA balancing will be enabled if running on a NUMA 750 machine. 751 752config NUMA_BALANCING 753 bool "Memory placement aware NUMA scheduler" 754 depends on ARCH_SUPPORTS_NUMA_BALANCING 755 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 756 depends on SMP && NUMA && MIGRATION 757 help 758 This option adds support for automatic NUMA aware memory/task placement. 759 The mechanism is quite primitive and is based on migrating memory when 760 it is references to the node the task is running on. 761 762 This system will be inactive on UMA systems. 763 764menuconfig CGROUPS 765 boolean "Control Group support" 766 depends on EVENTFD 767 help 768 This option adds support for grouping sets of processes together, for 769 use with process control subsystems such as Cpusets, CFS, memory 770 controls or device isolation. 771 See 772 - Documentation/scheduler/sched-design-CFS.txt (CFS) 773 - Documentation/cgroups/ (features for grouping, isolation 774 and resource control) 775 776 Say N if unsure. 777 778if CGROUPS 779 780config CGROUP_DEBUG 781 bool "Example debug cgroup subsystem" 782 default n 783 help 784 This option enables a simple cgroup subsystem that 785 exports useful debugging information about the cgroups 786 framework. 787 788 Say N if unsure. 789 790config CGROUP_FREEZER 791 bool "Freezer cgroup subsystem" 792 help 793 Provides a way to freeze and unfreeze all tasks in a 794 cgroup. 795 796config CGROUP_DEVICE 797 bool "Device controller for cgroups" 798 help 799 Provides a cgroup implementing whitelists for devices which 800 a process in the cgroup can mknod or open. 801 802config CPUSETS 803 bool "Cpuset support" 804 help 805 This option will let you create and manage CPUSETs which 806 allow dynamically partitioning a system into sets of CPUs and 807 Memory Nodes and assigning tasks to run only within those sets. 808 This is primarily useful on large SMP or NUMA systems. 809 810 Say N if unsure. 811 812config PROC_PID_CPUSET 813 bool "Include legacy /proc/<pid>/cpuset file" 814 depends on CPUSETS 815 default y 816 817config CGROUP_CPUACCT 818 bool "Simple CPU accounting cgroup subsystem" 819 help 820 Provides a simple Resource Controller for monitoring the 821 total CPU consumed by the tasks in a cgroup. 822 823config RESOURCE_COUNTERS 824 bool "Resource counters" 825 help 826 This option enables controller independent resource accounting 827 infrastructure that works with cgroups. 828 829config MEMCG 830 bool "Memory Resource Controller for Control Groups" 831 depends on RESOURCE_COUNTERS 832 select MM_OWNER 833 help 834 Provides a memory resource controller that manages both anonymous 835 memory and page cache. (See Documentation/cgroups/memory.txt) 836 837 Note that setting this option increases fixed memory overhead 838 associated with each page of memory in the system. By this, 839 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 840 usage tracking struct at boot. Total amount of this is printed out 841 at boot. 842 843 Only enable when you're ok with these trade offs and really 844 sure you need the memory resource controller. Even when you enable 845 this, you can set "cgroup_disable=memory" at your boot option to 846 disable memory resource controller and you can avoid overheads. 847 (and lose benefits of memory resource controller) 848 849 This config option also selects MM_OWNER config option, which 850 could in turn add some fork/exit overhead. 851 852config MEMCG_SWAP 853 bool "Memory Resource Controller Swap Extension" 854 depends on MEMCG && SWAP 855 help 856 Add swap management feature to memory resource controller. When you 857 enable this, you can limit mem+swap usage per cgroup. In other words, 858 when you disable this, memory resource controller has no cares to 859 usage of swap...a process can exhaust all of the swap. This extension 860 is useful when you want to avoid exhaustion swap but this itself 861 adds more overheads and consumes memory for remembering information. 862 Especially if you use 32bit system or small memory system, please 863 be careful about enabling this. When memory resource controller 864 is disabled by boot option, this will be automatically disabled and 865 there will be no overhead from this. Even when you set this config=y, 866 if boot option "swapaccount=0" is set, swap will not be accounted. 867 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 868 size is 4096bytes, 512k per 1Gbytes of swap. 869config MEMCG_SWAP_ENABLED 870 bool "Memory Resource Controller Swap Extension enabled by default" 871 depends on MEMCG_SWAP 872 default y 873 help 874 Memory Resource Controller Swap Extension comes with its price in 875 a bigger memory consumption. General purpose distribution kernels 876 which want to enable the feature but keep it disabled by default 877 and let the user enable it by swapaccount boot command line 878 parameter should have this option unselected. 879 For those who want to have the feature enabled by default should 880 select this option (if, for some reason, they need to disable it 881 then swapaccount=0 does the trick). 882config MEMCG_KMEM 883 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)" 884 depends on MEMCG && EXPERIMENTAL 885 depends on SLUB || SLAB 886 help 887 The Kernel Memory extension for Memory Resource Controller can limit 888 the amount of memory used by kernel objects in the system. Those are 889 fundamentally different from the entities handled by the standard 890 Memory Controller, which are page-based, and can be swapped. Users of 891 the kmem extension can use it to guarantee that no group of processes 892 will ever exhaust kernel resources alone. 893 894config CGROUP_HUGETLB 895 bool "HugeTLB Resource Controller for Control Groups" 896 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL 897 default n 898 help 899 Provides a cgroup Resource Controller for HugeTLB pages. 900 When you enable this, you can put a per cgroup limit on HugeTLB usage. 901 The limit is enforced during page fault. Since HugeTLB doesn't 902 support page reclaim, enforcing the limit at page fault time implies 903 that, the application will get SIGBUS signal if it tries to access 904 HugeTLB pages beyond its limit. This requires the application to know 905 beforehand how much HugeTLB pages it would require for its use. The 906 control group is tracked in the third page lru pointer. This means 907 that we cannot use the controller with huge page less than 3 pages. 908 909config CGROUP_PERF 910 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 911 depends on PERF_EVENTS && CGROUPS 912 help 913 This option extends the per-cpu mode to restrict monitoring to 914 threads which belong to the cgroup specified and run on the 915 designated cpu. 916 917 Say N if unsure. 918 919menuconfig CGROUP_SCHED 920 bool "Group CPU scheduler" 921 default n 922 help 923 This feature lets CPU scheduler recognize task groups and control CPU 924 bandwidth allocation to such task groups. It uses cgroups to group 925 tasks. 926 927if CGROUP_SCHED 928config FAIR_GROUP_SCHED 929 bool "Group scheduling for SCHED_OTHER" 930 depends on CGROUP_SCHED 931 default CGROUP_SCHED 932 933config CFS_BANDWIDTH 934 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 935 depends on EXPERIMENTAL 936 depends on FAIR_GROUP_SCHED 937 default n 938 help 939 This option allows users to define CPU bandwidth rates (limits) for 940 tasks running within the fair group scheduler. Groups with no limit 941 set are considered to be unconstrained and will run with no 942 restriction. 943 See tip/Documentation/scheduler/sched-bwc.txt for more information. 944 945config RT_GROUP_SCHED 946 bool "Group scheduling for SCHED_RR/FIFO" 947 depends on EXPERIMENTAL 948 depends on CGROUP_SCHED 949 default n 950 help 951 This feature lets you explicitly allocate real CPU bandwidth 952 to task groups. If enabled, it will also make it impossible to 953 schedule realtime tasks for non-root users until you allocate 954 realtime bandwidth for them. 955 See Documentation/scheduler/sched-rt-group.txt for more information. 956 957endif #CGROUP_SCHED 958 959config BLK_CGROUP 960 bool "Block IO controller" 961 depends on BLOCK 962 default n 963 ---help--- 964 Generic block IO controller cgroup interface. This is the common 965 cgroup interface which should be used by various IO controlling 966 policies. 967 968 Currently, CFQ IO scheduler uses it to recognize task groups and 969 control disk bandwidth allocation (proportional time slice allocation) 970 to such task groups. It is also used by bio throttling logic in 971 block layer to implement upper limit in IO rates on a device. 972 973 This option only enables generic Block IO controller infrastructure. 974 One needs to also enable actual IO controlling logic/policy. For 975 enabling proportional weight division of disk bandwidth in CFQ, set 976 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 977 CONFIG_BLK_DEV_THROTTLING=y. 978 979 See Documentation/cgroups/blkio-controller.txt for more information. 980 981config DEBUG_BLK_CGROUP 982 bool "Enable Block IO controller debugging" 983 depends on BLK_CGROUP 984 default n 985 ---help--- 986 Enable some debugging help. Currently it exports additional stat 987 files in a cgroup which can be useful for debugging. 988 989endif # CGROUPS 990 991config CHECKPOINT_RESTORE 992 bool "Checkpoint/restore support" if EXPERT 993 default n 994 help 995 Enables additional kernel features in a sake of checkpoint/restore. 996 In particular it adds auxiliary prctl codes to setup process text, 997 data and heap segment sizes, and a few additional /proc filesystem 998 entries. 999 1000 If unsure, say N here.
1001 1002menuconfig NAMESPACES 1003 bool "Namespaces support" if EXPERT 1004 default !EXPERT 1005 help 1006 Provides the way to make tasks work with different objects using 1007 the same id. For example same IPC id may refer to different objects 1008 or same user id or pid may refer to different tasks when used in 1009 different namespaces. 1010 1011if NAMESPACES 1012 1013config UTS_NS 1014 bool "UTS namespace" 1015 default y 1016 help 1017 In this namespace tasks see different info provided with the 1018 uname() system call 1019 1020config IPC_NS 1021 bool "IPC namespace" 1022 depends on (SYSVIPC || POSIX_MQUEUE) 1023 default y 1024 help 1025 In this namespace tasks work with IPC ids which correspond to 1026 different IPC objects in different namespaces. 1027 1028config USER_NS 1029 bool "User namespace (EXPERIMENTAL)" 1030 depends on EXPERIMENTAL 1031 depends on UIDGID_CONVERTED 1032 select UIDGID_STRICT_TYPE_CHECKS 1033 1034 default n 1035 help 1036 This allows containers, i.e. vservers, to use user namespaces 1037 to provide different user info for different servers. 1038 If unsure, say N. 1039 1040config PID_NS 1041 bool "PID Namespaces" 1042 default y 1043 help 1044 Support process id namespaces. This allows having multiple 1045 processes with the same pid as long as they are in different 1046 pid namespaces. This is a building block of containers. 1047 1048config NET_NS 1049 bool "Network namespace" 1050 depends on NET 1051 default y 1052 help 1053 Allow user space to create what appear to be multiple instances 1054 of the network stack. 1055 1056endif # NAMESPACES 1057 1058config UIDGID_CONVERTED 1059 # True if all of the selected software conmponents are known 1060 # to have uid_t and gid_t converted to kuid_t and kgid_t 1061 # where appropriate and are otherwise safe to use with 1062 # the user namespace. 1063 bool 1064 default y 1065 1066 # Networking 1067 depends on NET_9P = n 1068 1069 # Filesystems 1070 depends on 9P_FS = n 1071 depends on AFS_FS = n 1072 depends on CEPH_FS = n 1073 depends on CIFS = n 1074 depends on CODA_FS = n 1075 depends on GFS2_FS = n 1076 depends on NCP_FS = n 1077 depends on NFSD = n 1078 depends on NFS_FS = n 1079 depends on OCFS2_FS = n 1080 depends on XFS_FS = n 1081 1082config UIDGID_STRICT_TYPE_CHECKS 1083 bool "Require conversions between uid/gids and their internal representation" 1084 depends on UIDGID_CONVERTED 1085 default n 1086 help 1087 While the nececessary conversions are being added to all subsystems this option allows 1088 the code to continue to build for unconverted subsystems. 1089 1090 Say Y here if you want the strict type checking enabled 1091 1092config SCHED_AUTOGROUP 1093 bool "Automatic process group scheduling" 1094 select EVENTFD 1095 select CGROUPS 1096 select CGROUP_SCHED 1097 select FAIR_GROUP_SCHED 1098 help 1099 This option optimizes the scheduler for common desktop workloads by 1100 automatically creating and populating task groups. This separation 1101 of workloads isolates aggressive CPU burners (like build jobs) from 1102 desktop applications. Task group autogeneration is currently based 1103 upon task session. 1104 1105config MM_OWNER 1106 bool 1107 1108config SYSFS_DEPRECATED 1109 bool "Enable deprecated sysfs features to support old userspace tools" 1110 depends on SYSFS 1111 default n 1112 help 1113 This option adds code that switches the layout of the "block" class 1114 devices, to not show up in /sys/class/block/, but only in 1115 /sys/block/. 1116 1117 This switch is only active when the sysfs.deprecated=1 boot option is 1118 passed or the SYSFS_DEPRECATED_V2 option is set. 1119 1120 This option allows new kernels to run on old distributions and tools, 1121 which might get confused by /sys/class/block/. Since 2007/2008 all 1122 major distributions and tools handle this just fine. 1123 1124 Recent distributions and userspace tools after 2009/2010 depend on 1125 the existence of /sys/class/block/, and will not work with this 1126 option enabled. 1127 1128 Only if you are using a new kernel on an old distribution, you might 1129 need to say Y here. 1130 1131config SYSFS_DEPRECATED_V2 1132 bool "Enable deprecated sysfs features by default" 1133 default n 1134 depends on SYSFS 1135 depends on SYSFS_DEPRECATED 1136 help 1137 Enable deprecated sysfs by default. 1138 1139 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1140 option. 1141 1142 Only if you are using a new kernel on an old distribution, you might 1143 need to say Y here. Even then, odds are you would not need it 1144 enabled, you can always pass the boot option if absolutely necessary. 1145 1146config RELAY 1147 bool "Kernel->user space relay support (formerly relayfs)" 1148 help 1149 This option enables support for relay interface support in 1150 certain file systems (such as debugfs). 1151 It is designed to provide an efficient mechanism for tools and 1152 facilities to relay large amounts of data from kernel space to 1153 user space. 1154 1155 If unsure, say N. 1156 1157config BLK_DEV_INITRD 1158 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1159 depends on BROKEN || !FRV 1160 help 1161 The initial RAM filesystem is a ramfs which is loaded by the 1162 boot loader (loadlin or lilo) and that is mounted as root 1163 before the normal boot procedure. It is typically used to 1164 load modules needed to mount the "real" root file system, 1165 etc. See <file:Documentation/initrd.txt> for details. 1166 1167 If RAM disk support (BLK_DEV_RAM) is also included, this 1168 also enables initial RAM disk (initrd) support and adds 1169 15 Kbytes (more on some other architectures) to the kernel size. 1170 1171 If unsure say Y. 1172 1173if BLK_DEV_INITRD 1174 1175source "usr/Kconfig" 1176 1177endif 1178 1179config CC_OPTIMIZE_FOR_SIZE 1180 bool "Optimize for size" 1181 help 1182 Enabling this option will pass "-Os" instead of "-O2" to gcc 1183 resulting in a smaller kernel. 1184 1185 If unsure, say N. 1186 1187config SYSCTL 1188 bool 1189 1190config ANON_INODES 1191 bool 1192 1193menuconfig EXPERT 1194 bool "Configure standard kernel features (expert users)" 1195 # Unhide debug options, to make the on-by-default options visible 1196 select DEBUG_KERNEL 1197 help 1198 This option allows certain base kernel options and settings 1199 to be disabled or tweaked. This is for specialized 1200 environments which can tolerate a "non-standard" kernel. 1201 Only use this if you really know what you are doing. 1202 1203config HAVE_UID16 1204 bool 1205 1206config UID16 1207 bool "Enable 16-bit UID system calls" if EXPERT 1208 depends on HAVE_UID16 1209 default y 1210 help 1211 This enables the legacy 16-bit UID syscall wrappers. 1212 1213config SYSCTL_SYSCALL 1214 bool "Sysctl syscall support" if EXPERT 1215 depends on PROC_SYSCTL 1216 default n 1217 select SYSCTL 1218 ---help--- 1219 sys_sysctl uses binary paths that have been found challenging 1220 to properly maintain and use. The interface in /proc/sys 1221 using paths with ascii names is now the primary path to this 1222 information. 1223 1224 Almost nothing using the binary sysctl interface so if you are 1225 trying to save some space it is probably safe to disable this, 1226 making your kernel marginally smaller. 1227 1228 If unsure say N here. 1229 1230config SYSCTL_EXCEPTION_TRACE 1231 bool 1232 help 1233 Enable support for /proc/sys/debug/exception-trace. 1234 1235config KALLSYMS 1236 bool "Load all symbols for debugging/ksymoops" if EXPERT 1237 default y 1238 help 1239 Say Y here to let the kernel print out symbolic crash information and 1240 symbolic stack backtraces. This increases the size of the kernel 1241 somewhat, as all symbols have to be loaded into the kernel image. 1242 1243config KALLSYMS_ALL 1244 bool "Include all symbols in kallsyms" 1245 depends on DEBUG_KERNEL && KALLSYMS 1246 help 1247 Normally kallsyms only contains the symbols of functions for nicer 1248 OOPS messages and backtraces (i.e., symbols from the text and inittext 1249 sections). This is sufficient for most cases. And only in very rare 1250 cases (e.g., when a debugger is used) all symbols are required (e.g., 1251 names of variables from the data sections, etc). 1252 1253 This option makes sure that all symbols are loaded into the kernel 1254 image (i.e., symbols from all sections) in cost of increased kernel 1255 size (depending on the kernel configuration, it may be 300KiB or 1256 something like this). 1257 1258 Say N unless you really need all symbols. 1259 1260config HOTPLUG 1261 def_bool y 1262 1263config PRINTK 1264 default y 1265 bool "Enable support for printk" if EXPERT 1266 help 1267 This option enables normal printk support. Removing it 1268 eliminates most of the message strings from the kernel image 1269 and makes the kernel more or less silent. As this makes it 1270 very difficult to diagnose system problems, saying N here is 1271 strongly discouraged. 1272 1273config BUG 1274 bool "BUG() support" if EXPERT 1275 default y 1276 help 1277 Disabling this option eliminates support for BUG and WARN, reducing 1278 the size of your kernel image and potentially quietly ignoring 1279 numerous fatal conditions. You should only consider disabling this 1280 option for embedded systems with no facilities for reporting errors. 1281 Just say Y. 1282 1283config ELF_CORE 1284 depends on COREDUMP 1285 default y 1286 bool "Enable ELF core dumps" if EXPERT 1287 help 1288 Enable support for generating core dumps. Disabling saves about 4k. 1289 1290 1291config PCSPKR_PLATFORM 1292 bool "Enable PC-Speaker support" if EXPERT 1293 depends on HAVE_PCSPKR_PLATFORM 1294 select I8253_LOCK 1295 default y 1296 help 1297 This option allows to disable the internal PC-Speaker 1298 support, saving some memory. 1299 1300config HAVE_PCSPKR_PLATFORM 1301 bool 1302 1303config BASE_FULL 1304 default y 1305 bool "Enable full-sized data structures for core" if EXPERT 1306 help 1307 Disabling this option reduces the size of miscellaneous core 1308 kernel data structures. This saves memory on small machines, 1309 but may reduce performance. 1310 1311config FUTEX 1312 bool "Enable futex support" if EXPERT 1313 default y 1314 select RT_MUTEXES 1315 help 1316 Disabling this option will cause the kernel to be built without 1317 support for "fast userspace mutexes". The resulting kernel may not 1318 run glibc-based applications correctly. 1319 1320config EPOLL 1321 bool "Enable eventpoll support" if EXPERT 1322 default y 1323 select ANON_INODES 1324 help 1325 Disabling this option will cause the kernel to be built without 1326 support for epoll family of system calls. 1327 1328config SIGNALFD 1329 bool "Enable signalfd() system call" if EXPERT 1330 select ANON_INODES 1331 default y 1332 help 1333 Enable the signalfd() system call that allows to receive signals 1334 on a file descriptor. 1335 1336 If unsure, say Y. 1337 1338config TIMERFD 1339 bool "Enable timerfd() system call" if EXPERT 1340 select ANON_INODES 1341 default y 1342 help 1343 Enable the timerfd() system call that allows to receive timer 1344 events on a file descriptor. 1345 1346 If unsure, say Y. 1347 1348config EVENTFD 1349 bool "Enable eventfd() system call" if EXPERT 1350 select ANON_INODES 1351 default y 1352 help 1353 Enable the eventfd() system call that allows to receive both 1354 kernel notification (ie. KAIO) or userspace notifications. 1355 1356 If unsure, say Y. 1357 1358config SHMEM 1359 bool "Use full shmem filesystem" if EXPERT 1360 default y 1361 depends on MMU 1362 help 1363 The shmem is an internal filesystem used to manage shared memory. 1364 It is backed by swap and manages resource limits. It is also exported 1365 to userspace as tmpfs if TMPFS is enabled. Disabling this 1366 option replaces shmem and tmpfs with the much simpler ramfs code, 1367 which may be appropriate on small systems without swap. 1368 1369config AIO 1370 bool "Enable AIO support" if EXPERT 1371 default y 1372 help 1373 This option enables POSIX asynchronous I/O which may by used 1374 by some high performance threaded applications. Disabling 1375 this option saves about 7k. 1376 1377config EMBEDDED 1378 bool "Embedded system" 1379 select EXPERT 1380 help 1381 This option should be enabled if compiling the kernel for 1382 an embedded system so certain expert options are available 1383 for configuration. 1384 1385config HAVE_PERF_EVENTS 1386 bool 1387 help 1388 See tools/perf/design.txt for details. 1389 1390config PERF_USE_VMALLOC 1391 bool 1392 help 1393 See tools/perf/design.txt for details 1394 1395menu "Kernel Performance Events And Counters" 1396 1397config PERF_EVENTS 1398 bool "Kernel performance events and counters" 1399 default y if PROFILING 1400 depends on HAVE_PERF_EVENTS 1401 select ANON_INODES 1402 select IRQ_WORK 1403 help 1404 Enable kernel support for various performance events provided 1405 by software and hardware. 1406 1407 Software events are supported either built-in or via the 1408 use of generic tracepoints. 1409 1410 Most modern CPUs support performance events via performance 1411 counter registers. These registers count the number of certain 1412 types of hw events: such as instructions executed, cachemisses 1413 suffered, or branches mis-predicted - without slowing down the 1414 kernel or applications. These registers can also trigger interrupts 1415 when a threshold number of events have passed - and can thus be 1416 used to profile the code that runs on that CPU. 1417 1418 The Linux Performance Event subsystem provides an abstraction of 1419 these software and hardware event capabilities, available via a 1420 system call and used by the "perf" utility in tools/perf/. It 1421 provides per task and per CPU counters, and it provides event 1422 capabilities on top of those. 1423 1424 Say Y if unsure. 1425 1426config DEBUG_PERF_USE_VMALLOC 1427 default n 1428 bool "Debug: use vmalloc to back perf mmap() buffers" 1429 depends on PERF_EVENTS && DEBUG_KERNEL 1430 select PERF_USE_VMALLOC 1431 help 1432 Use vmalloc memory to back perf mmap() buffers. 1433 1434 Mostly useful for debugging the vmalloc code on platforms 1435 that don't require it. 1436 1437 Say N if unsure. 1438 1439endmenu 1440 1441config VM_EVENT_COUNTERS 1442 default y 1443 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1444 help 1445 VM event counters are needed for event counts to be shown. 1446 This option allows the disabling of the VM event counters 1447 on EXPERT systems. /proc/vmstat will only show page counts 1448 if VM event counters are disabled. 1449 1450config PCI_QUIRKS 1451 default y 1452 bool "Enable PCI quirk workarounds" if EXPERT 1453 depends on PCI 1454 help 1455 This enables workarounds for various PCI chipset 1456 bugs/quirks. Disable this only if your target machine is 1457 unaffected by PCI quirks. 1458 1459config SLUB_DEBUG 1460 default y 1461 bool "Enable SLUB debugging support" if EXPERT 1462 depends on SLUB && SYSFS 1463 help 1464 SLUB has extensive debug support features. Disabling these can 1465 result in significant savings in code size. This also disables 1466 SLUB sysfs support. /sys/slab will not exist and there will be 1467 no support for cache validation etc. 1468 1469config COMPAT_BRK 1470 bool "Disable heap randomization" 1471 default y 1472 help 1473 Randomizing heap placement makes heap exploits harder, but it 1474 also breaks ancient binaries (including anything libc5 based). 1475 This option changes the bootup default to heap randomization 1476 disabled, and can be overridden at runtime by setting 1477 /proc/sys/kernel/randomize_va_space to 2. 1478 1479 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1480 1481choice 1482 prompt "Choose SLAB allocator" 1483 default SLUB 1484 help 1485 This option allows to select a slab allocator. 1486 1487config SLAB 1488 bool "SLAB" 1489 help 1490 The regular slab allocator that is established and known to work 1491 well in all environments. It organizes cache hot objects in 1492 per cpu and per node queues. 1493 1494config SLUB 1495 bool "SLUB (Unqueued Allocator)" 1496 help 1497 SLUB is a slab allocator that minimizes cache line usage 1498 instead of managing queues of cached objects (SLAB approach). 1499 Per cpu caching is realized using slabs of objects instead 1500 of queues of objects. SLUB can use memory efficiently 1501 and has enhanced diagnostics. SLUB is the default choice for 1502 a slab allocator. 1503 1504config SLOB 1505 depends on EXPERT 1506 bool "SLOB (Simple Allocator)" 1507 help 1508 SLOB replaces the stock allocator with a drastically simpler 1509 allocator. SLOB is generally more space efficient but 1510 does not perform as well on large systems. 1511 1512endchoice 1513 1514config MMAP_ALLOW_UNINITIALIZED 1515 bool "Allow mmapped anonymous memory to be uninitialized" 1516 depends on EXPERT && !MMU 1517 default n 1518 help 1519 Normally, and according to the Linux spec, anonymous memory obtained 1520 from mmap() has it's contents cleared before it is passed to 1521 userspace. Enabling this config option allows you to request that 1522 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1523 providing a huge performance boost. If this option is not enabled, 1524 then the flag will be ignored. 1525 1526 This is taken advantage of by uClibc's malloc(), and also by 1527 ELF-FDPIC binfmt's brk and stack allocator. 1528 1529 Because of the obvious security issues, this option should only be 1530 enabled on embedded devices where you control what is run in 1531 userspace. Since that isn't generally a problem on no-MMU systems, 1532 it is normally safe to say Y here. 1533 1534 See Documentation/nommu-mmap.txt for more information. 1535 1536config PROFILING 1537 bool "Profiling support" 1538 help 1539 Say Y here to enable the extended profiling support mechanisms used 1540 by profilers such as OProfile. 1541 1542# 1543# Place an empty function call at each tracepoint site. Can be 1544# dynamically changed for a probe function. 1545# 1546config TRACEPOINTS 1547 bool 1548 1549source "arch/Kconfig" 1550 1551endmenu # General setup 1552 1553config HAVE_GENERIC_DMA_COHERENT 1554 bool 1555 default n 1556 1557config SLABINFO 1558 bool 1559 depends on PROC_FS 1560 depends on SLAB || SLUB_DEBUG 1561 default y 1562 1563config RT_MUTEXES 1564 boolean 1565 1566config BASE_SMALL 1567 int 1568 default 0 if BASE_FULL 1569 default 1 if !BASE_FULL 1570 1571menuconfig MODULES 1572 bool "Enable loadable module support" 1573 help 1574 Kernel modules are small pieces of compiled code which can 1575 be inserted in the running kernel, rather than being 1576 permanently built into the kernel. You use the "modprobe" 1577 tool to add (and sometimes remove) them. If you say Y here, 1578 many parts of the kernel can be built as modules (by 1579 answering M instead of Y where indicated): this is most 1580 useful for infrequently used options which are not required 1581 for booting. For more information, see the man pages for 1582 modprobe, lsmod, modinfo, insmod and rmmod. 1583 1584 If you say Y here, you will need to run "make 1585 modules_install" to put the modules under /lib/modules/ 1586 where modprobe can find them (you may need to be root to do 1587 this). 1588 1589 If unsure, say Y. 1590 1591if MODULES 1592 1593config MODULE_FORCE_LOAD 1594 bool "Forced module loading" 1595 default n 1596 help 1597 Allow loading of modules without version information (ie. modprobe 1598 --force). Forced module loading sets the 'F' (forced) taint flag and 1599 is usually a really bad idea. 1600 1601config MODULE_UNLOAD 1602 bool "Module unloading" 1603 help 1604 Without this option you will not be able to unload any 1605 modules (note that some modules may not be unloadable 1606 anyway), which makes your kernel smaller, faster 1607 and simpler. If unsure, say Y. 1608 1609config MODULE_FORCE_UNLOAD 1610 bool "Forced module unloading" 1611 depends on MODULE_UNLOAD && EXPERIMENTAL 1612 help 1613 This option allows you to force a module to unload, even if the 1614 kernel believes it is unsafe: the kernel will remove the module 1615 without waiting for anyone to stop using it (using the -f option to 1616 rmmod). This is mainly for kernel developers and desperate users. 1617 If unsure, say N. 1618 1619config MODVERSIONS 1620 bool "Module versioning support" 1621 help 1622 Usually, you have to use modules compiled with your kernel. 1623 Saying Y here makes it sometimes possible to use modules 1624 compiled for different kernels, by adding enough information 1625 to the modules to (hopefully) spot any changes which would 1626 make them incompatible with the kernel you are running. If 1627 unsure, say N. 1628 1629config MODULE_SRCVERSION_ALL 1630 bool "Source checksum for all modules" 1631 help 1632 Modules which contain a MODULE_VERSION get an extra "srcversion" 1633 field inserted into their modinfo section, which contains a 1634 sum of the source files which made it. This helps maintainers 1635 see exactly which source was used to build a module (since 1636 others sometimes change the module source without updating 1637 the version). With this option, such a "srcversion" field 1638 will be created for all modules. If unsure, say N. 1639 1640config MODULE_SIG 1641 bool "Module signature verification" 1642 depends on MODULES 1643 select KEYS 1644 select CRYPTO 1645 select ASYMMETRIC_KEY_TYPE 1646 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1647 select PUBLIC_KEY_ALGO_RSA 1648 select ASN1 1649 select OID_REGISTRY 1650 select X509_CERTIFICATE_PARSER 1651 help 1652 Check modules for valid signatures upon load: the signature 1653 is simply appended to the module. For more information see 1654 Documentation/module-signing.txt. 1655 1656 !!!WARNING!!! If you enable this option, you MUST make sure that the 1657 module DOES NOT get stripped after being signed. This includes the 1658 debuginfo strip done by some packagers (such as rpmbuild) and 1659 inclusion into an initramfs that wants the module size reduced. 1660 1661config MODULE_SIG_FORCE 1662 bool "Require modules to be validly signed" 1663 depends on MODULE_SIG 1664 help 1665 Reject unsigned modules or signed modules for which we don't have a 1666 key. Without this, such modules will simply taint the kernel. 1667 1668choice 1669 prompt "Which hash algorithm should modules be signed with?" 1670 depends on MODULE_SIG 1671 help 1672 This determines which sort of hashing algorithm will be used during 1673 signature generation. This algorithm _must_ be built into the kernel 1674 directly so that signature verification can take place. It is not 1675 possible to load a signed module containing the algorithm to check 1676 the signature on that module. 1677 1678config MODULE_SIG_SHA1 1679 bool "Sign modules with SHA-1" 1680 select CRYPTO_SHA1 1681 1682config MODULE_SIG_SHA224 1683 bool "Sign modules with SHA-224" 1684 select CRYPTO_SHA256 1685 1686config MODULE_SIG_SHA256 1687 bool "Sign modules with SHA-256" 1688 select CRYPTO_SHA256 1689 1690config MODULE_SIG_SHA384 1691 bool "Sign modules with SHA-384" 1692 select CRYPTO_SHA512 1693 1694config MODULE_SIG_SHA512 1695 bool "Sign modules with SHA-512" 1696 select CRYPTO_SHA512 1697 1698endchoice 1699 1700endif # MODULES 1701 1702config INIT_ALL_POSSIBLE 1703 bool 1704 help 1705 Back when each arch used to define their own cpu_online_mask and 1706 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1707 with all 1s, and others with all 0s. When they were centralised, 1708 it was better to provide this option than to break all the archs 1709 and have several arch maintainers pursuing me down dark alleys. 1710 1711config STOP_MACHINE 1712 bool 1713 default y 1714 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1715 help 1716 Need stop_machine() primitive. 1717 1718source "block/Kconfig" 1719 1720config PREEMPT_NOTIFIERS 1721 bool 1722 1723config PADATA 1724 depends on SMP 1725 bool 1726 1727# Can be selected by architectures with broken toolchains 1728# that get confused by correct const<->read_only section 1729# mappings 1730config BROKEN_RODATA 1731 bool 1732 1733config ASN1 1734 tristate 1735 help 1736 Build a simple ASN.1 grammar compiler that produces a bytecode output 1737 that can be interpreted by the ASN.1 stream decoder and used to 1738 inform it as to what tags are to be expected in a stream and what 1739 functions to call on what tags. 1740 1741source "kernel/Kconfig.locks" 1742