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 default y 23 24menu "General setup" 25 26config EXPERIMENTAL 27 bool "Prompt for development and/or incomplete code/drivers" 28 ---help--- 29 Some of the various things that Linux supports (such as network 30 drivers, file systems, network protocols, etc.) can be in a state 31 of development where the functionality, stability, or the level of 32 testing is not yet high enough for general use. This is usually 33 known as the "alpha-test" phase among developers. If a feature is 34 currently in alpha-test, then the developers usually discourage 35 uninformed widespread use of this feature by the general public to 36 avoid "Why doesn't this work?" type mail messages. However, active 37 testing and use of these systems is welcomed. Just be aware that it 38 may not meet the normal level of reliability or it may fail to work 39 in some special cases. Detailed bug reports from people familiar 40 with the kernel internals are usually welcomed by the developers 41 (before submitting bug reports, please read the documents 42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 43 <file:Documentation/BUG-HUNTING>, and 44 <file:Documentation/oops-tracing.txt> in the kernel source). 45 46 This option will also make obsoleted drivers available. These are 47 drivers that have been replaced by something else, and/or are 48 scheduled to be removed in a future kernel release. 49 50 Unless you intend to help test and develop a feature or driver that 51 falls into this category, or you have a situation that requires 52 using these features, you should probably say N here, which will 53 cause the configurator to present you with fewer choices. If 54 you say Y here, you will be offered the choice of using features or 55 drivers that are currently considered to be in the alpha-test phase. 56 57config BROKEN 58 bool 59 60config BROKEN_ON_SMP 61 bool 62 depends on BROKEN || !SMP 63 default y 64 65config LOCK_KERNEL 66 bool 67 depends on SMP || PREEMPT 68 default y 69 70config INIT_ENV_ARG_LIMIT 71 int 72 default 32 if !UML 73 default 128 if UML 74 help 75 Maximum of each of the number of arguments and environment 76 variables passed to init from the kernel command line. 77 78 79config LOCALVERSION 80 string "Local version - append to kernel release" 81 help 82 Append an extra string to the end of your kernel version. 83 This will show up when you type uname, for example. 84 The string you set here will be appended after the contents of 85 any files with a filename matching localversion* in your 86 object and source tree, in that order. Your total string can 87 be a maximum of 64 characters. 88 89config LOCALVERSION_AUTO 90 bool "Automatically append version information to the version string" 91 default y 92 help 93 This will try to automatically determine if the current tree is a 94 release tree by looking for git tags that belong to the current 95 top of tree revision. 96 97 A string of the format -gxxxxxxxx will be added to the localversion 98 if a git-based tree is found. The string generated by this will be 99 appended after any matching localversion* files, and after the value 100 set in CONFIG_LOCALVERSION. 101 102 (The actual string used here is the first eight characters produced 103 by running the command: 104 105 $ git rev-parse --verify HEAD 106 107 which is done within the script "scripts/setlocalversion".) 108 109config HAVE_KERNEL_GZIP 110 bool 111 112config HAVE_KERNEL_BZIP2 113 bool 114 115config HAVE_KERNEL_LZMA 116 bool 117 118config HAVE_KERNEL_LZO 119 bool 120 121choice 122 prompt "Kernel compression mode" 123 default KERNEL_GZIP 124 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO 125 help 126 The linux kernel is a kind of self-extracting executable. 127 Several compression algorithms are available, which differ 128 in efficiency, compression and decompression speed. 129 Compression speed is only relevant when building a kernel. 130 Decompression speed is relevant at each boot. 131 132 If you have any problems with bzip2 or lzma compressed 133 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 134 version of this functionality (bzip2 only), for 2.4, was 135 supplied by Christian Ludwig) 136 137 High compression options are mostly useful for users, who 138 are low on disk space (embedded systems), but for whom ram 139 size matters less. 140 141 If in doubt, select 'gzip' 142 143config KERNEL_GZIP 144 bool "Gzip" 145 depends on HAVE_KERNEL_GZIP 146 help 147 The old and tried gzip compression. It provides a good balance 148 between compression ratio and decompression speed. 149 150config KERNEL_BZIP2 151 bool "Bzip2" 152 depends on HAVE_KERNEL_BZIP2 153 help 154 Its compression ratio and speed is intermediate. 155 Decompression speed is slowest among the three. The kernel 156 size is about 10% smaller with bzip2, in comparison to gzip. 157 Bzip2 uses a large amount of memory. For modern kernels you 158 will need at least 8MB RAM or more for booting. 159 160config KERNEL_LZMA 161 bool "LZMA" 162 depends on HAVE_KERNEL_LZMA 163 help 164 The most recent compression algorithm. 165 Its ratio is best, decompression speed is between the other 166 two. Compression is slowest. The kernel size is about 33% 167 smaller with LZMA in comparison to gzip. 168 169config KERNEL_LZO 170 bool "LZO" 171 depends on HAVE_KERNEL_LZO 172 help 173 Its compression ratio is the poorest among the 4. The kernel 174 size is about about 10% bigger than gzip; however its speed 175 (both compression and decompression) is the fastest. 176 177endchoice 178 179config SWAP 180 bool "Support for paging of anonymous memory (swap)" 181 depends on MMU && BLOCK 182 default y 183 help 184 This option allows you to choose whether you want to have support 185 for so called swap devices or swap files in your kernel that are 186 used to provide more virtual memory than the actual RAM present 187 in your computer. If unsure say Y. 188 189config SYSVIPC 190 bool "System V IPC" 191 ---help--- 192 Inter Process Communication is a suite of library functions and 193 system calls which let processes (running programs) synchronize and 194 exchange information. It is generally considered to be a good thing, 195 and some programs won't run unless you say Y here. In particular, if 196 you want to run the DOS emulator dosemu under Linux (read the 197 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 198 you'll need to say Y here. 199 200 You can find documentation about IPC with "info ipc" and also in 201 section 6.4 of the Linux Programmer's Guide, available from 202 <http://www.tldp.org/guides.html>. 203 204config SYSVIPC_SYSCTL 205 bool 206 depends on SYSVIPC 207 depends on SYSCTL 208 default y 209 210config POSIX_MQUEUE 211 bool "POSIX Message Queues" 212 depends on NET && EXPERIMENTAL 213 ---help--- 214 POSIX variant of message queues is a part of IPC. In POSIX message 215 queues every message has a priority which decides about succession 216 of receiving it by a process. If you want to compile and run 217 programs written e.g. for Solaris with use of its POSIX message 218 queues (functions mq_*) say Y here. 219 220 POSIX message queues are visible as a filesystem called 'mqueue' 221 and can be mounted somewhere if you want to do filesystem 222 operations on message queues. 223 224 If unsure, say Y. 225 226config POSIX_MQUEUE_SYSCTL 227 bool 228 depends on POSIX_MQUEUE 229 depends on SYSCTL 230 default y 231 232config BSD_PROCESS_ACCT 233 bool "BSD Process Accounting" 234 help 235 If you say Y here, a user level program will be able to instruct the 236 kernel (via a special system call) to write process accounting 237 information to a file: whenever a process exits, information about 238 that process will be appended to the file by the kernel. The 239 information includes things such as creation time, owning user, 240 command name, memory usage, controlling terminal etc. (the complete 241 list is in the struct acct in <file:include/linux/acct.h>). It is 242 up to the user level program to do useful things with this 243 information. This is generally a good idea, so say Y. 244 245config BSD_PROCESS_ACCT_V3 246 bool "BSD Process Accounting version 3 file format" 247 depends on BSD_PROCESS_ACCT 248 default n 249 help 250 If you say Y here, the process accounting information is written 251 in a new file format that also logs the process IDs of each 252 process and it's parent. Note that this file format is incompatible 253 with previous v0/v1/v2 file formats, so you will need updated tools 254 for processing it. A preliminary version of these tools is available 255 at <http://www.gnu.org/software/acct/>. 256 257config TASKSTATS 258 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 259 depends on NET 260 default n 261 help 262 Export selected statistics for tasks/processes through the 263 generic netlink interface. Unlike BSD process accounting, the 264 statistics are available during the lifetime of tasks/processes as 265 responses to commands. Like BSD accounting, they are sent to user 266 space on task exit. 267 268 Say N if unsure. 269 270config TASK_DELAY_ACCT 271 bool "Enable per-task delay accounting (EXPERIMENTAL)" 272 depends on TASKSTATS 273 help 274 Collect information on time spent by a task waiting for system 275 resources like cpu, synchronous block I/O completion and swapping 276 in pages. Such statistics can help in setting a task's priorities 277 relative to other tasks for cpu, io, rss limits etc. 278 279 Say N if unsure. 280 281config TASK_XACCT 282 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 283 depends on TASKSTATS 284 help 285 Collect extended task accounting data and send the data 286 to userland for processing over the taskstats interface. 287 288 Say N if unsure. 289 290config TASK_IO_ACCOUNTING 291 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 292 depends on TASK_XACCT 293 help 294 Collect information on the number of bytes of storage I/O which this 295 task has caused. 296 297 Say N if unsure. 298 299config AUDIT 300 bool "Auditing support" 301 depends on NET 302 help 303 Enable auditing infrastructure that can be used with another 304 kernel subsystem, such as SELinux (which requires this for 305 logging of avc messages output). Does not do system-call 306 auditing without CONFIG_AUDITSYSCALL. 307 308config AUDITSYSCALL 309 bool "Enable system-call auditing support" 310 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH) 311 default y if SECURITY_SELINUX 312 help 313 Enable low-overhead system-call auditing infrastructure that 314 can be used independently or with another kernel subsystem, 315 such as SELinux. To use audit's filesystem watch feature, please 316 ensure that INOTIFY is configured. 317 318config AUDIT_TREE 319 def_bool y 320 depends on AUDITSYSCALL 321 select INOTIFY 322 323menu "RCU Subsystem" 324 325choice 326 prompt "RCU Implementation" 327 default TREE_RCU 328 329config TREE_RCU 330 bool "Tree-based hierarchical RCU" 331 help 332 This option selects the RCU implementation that is 333 designed for very large SMP system with hundreds or 334 thousands of CPUs. It also scales down nicely to 335 smaller systems. 336 337config TREE_PREEMPT_RCU 338 bool "Preemptable tree-based hierarchical RCU" 339 depends on PREEMPT 340 help 341 This option selects the RCU implementation that is 342 designed for very large SMP systems with hundreds or 343 thousands of CPUs, but for which real-time response 344 is also required. It also scales down nicely to 345 smaller systems. 346 347config TINY_RCU 348 bool "UP-only small-memory-footprint RCU" 349 depends on !SMP 350 help 351 This option selects the RCU implementation that is 352 designed for UP systems from which real-time response 353 is not required. This option greatly reduces the 354 memory footprint of RCU. 355 356endchoice 357 358config RCU_TRACE 359 bool "Enable tracing for RCU" 360 depends on TREE_RCU || TREE_PREEMPT_RCU 361 help 362 This option provides tracing in RCU which presents stats 363 in debugfs for debugging RCU implementation. 364 365 Say Y here if you want to enable RCU tracing 366 Say N if you are unsure. 367 368config RCU_FANOUT 369 int "Tree-based hierarchical RCU fanout value" 370 range 2 64 if 64BIT 371 range 2 32 if !64BIT 372 depends on TREE_RCU || TREE_PREEMPT_RCU 373 default 64 if 64BIT 374 default 32 if !64BIT 375 help 376 This option controls the fanout of hierarchical implementations 377 of RCU, allowing RCU to work efficiently on machines with 378 large numbers of CPUs. This value must be at least the cube 379 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit 380 systems and up to 262,144 for 64-bit systems. 381 382 Select a specific number if testing RCU itself. 383 Take the default if unsure. 384 385config RCU_FANOUT_EXACT 386 bool "Disable tree-based hierarchical RCU auto-balancing" 387 depends on TREE_RCU || TREE_PREEMPT_RCU 388 default n 389 help 390 This option forces use of the exact RCU_FANOUT value specified, 391 regardless of imbalances in the hierarchy. This is useful for 392 testing RCU itself, and might one day be useful on systems with 393 strong NUMA behavior. 394 395 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 396 397 Say N if unsure. 398 399config TREE_RCU_TRACE 400 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 401 select DEBUG_FS 402 help 403 This option provides tracing for the TREE_RCU and 404 TREE_PREEMPT_RCU implementations, permitting Makefile to 405 trivially select kernel/rcutree_trace.c. 406 407endmenu # "RCU Subsystem" 408 409config IKCONFIG 410 tristate "Kernel .config support" 411 ---help--- 412 This option enables the complete Linux kernel ".config" file 413 contents to be saved in the kernel. It provides documentation 414 of which kernel options are used in a running kernel or in an 415 on-disk kernel. This information can be extracted from the kernel 416 image file with the script scripts/extract-ikconfig and used as 417 input to rebuild the current kernel or to build another kernel. 418 It can also be extracted from a running kernel by reading 419 /proc/config.gz if enabled (below). 420 421config IKCONFIG_PROC 422 bool "Enable access to .config through /proc/config.gz" 423 depends on IKCONFIG && PROC_FS 424 ---help--- 425 This option enables access to the kernel configuration file 426 through /proc/config.gz. 427 428config LOG_BUF_SHIFT 429 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 430 range 12 21 431 default 17 432 help 433 Select kernel log buffer size as a power of 2. 434 Examples: 435 17 => 128 KB 436 16 => 64 KB 437 15 => 32 KB 438 14 => 16 KB 439 13 => 8 KB 440 12 => 4 KB 441 442# 443# Architectures with an unreliable sched_clock() should select this: 444# 445config HAVE_UNSTABLE_SCHED_CLOCK 446 bool 447 448config GROUP_SCHED 449 bool "Group CPU scheduler" 450 depends on EXPERIMENTAL 451 default n 452 help 453 This feature lets CPU scheduler recognize task groups and control CPU 454 bandwidth allocation to such task groups. 455 In order to create a group from arbitrary set of processes, use 456 CONFIG_CGROUPS. (See Control Group support.) 457 458config FAIR_GROUP_SCHED 459 bool "Group scheduling for SCHED_OTHER" 460 depends on GROUP_SCHED 461 default GROUP_SCHED 462 463config RT_GROUP_SCHED 464 bool "Group scheduling for SCHED_RR/FIFO" 465 depends on EXPERIMENTAL 466 depends on GROUP_SCHED 467 default n 468 help 469 This feature lets you explicitly allocate real CPU bandwidth 470 to users or control groups (depending on the "Basis for grouping tasks" 471 setting below. If enabled, it will also make it impossible to 472 schedule realtime tasks for non-root users until you allocate 473 realtime bandwidth for them. 474 See Documentation/scheduler/sched-rt-group.txt for more information. 475 476choice 477 depends on GROUP_SCHED 478 prompt "Basis for grouping tasks" 479 default USER_SCHED 480 481config USER_SCHED 482 bool "user id" 483 help 484 This option will choose userid as the basis for grouping 485 tasks, thus providing equal CPU bandwidth to each user. 486 487config CGROUP_SCHED 488 bool "Control groups" 489 depends on CGROUPS 490 help 491 This option allows you to create arbitrary task groups 492 using the "cgroup" pseudo filesystem and control 493 the cpu bandwidth allocated to each such task group. 494 Refer to Documentation/cgroups/cgroups.txt for more 495 information on "cgroup" pseudo filesystem. 496 497endchoice 498 499menuconfig CGROUPS 500 boolean "Control Group support" 501 help 502 This option adds support for grouping sets of processes together, for 503 use with process control subsystems such as Cpusets, CFS, memory 504 controls or device isolation. 505 See 506 - Documentation/scheduler/sched-design-CFS.txt (CFS) 507 - Documentation/cgroups/ (features for grouping, isolation 508 and resource control) 509 510 Say N if unsure. 511 512if CGROUPS 513 514config CGROUP_DEBUG 515 bool "Example debug cgroup subsystem" 516 depends on CGROUPS 517 default n 518 help 519 This option enables a simple cgroup subsystem that 520 exports useful debugging information about the cgroups 521 framework. 522 523 Say N if unsure. 524 525config CGROUP_NS 526 bool "Namespace cgroup subsystem" 527 depends on CGROUPS 528 help 529 Provides a simple namespace cgroup subsystem to 530 provide hierarchical naming of sets of namespaces, 531 for instance virtual servers and checkpoint/restart 532 jobs. 533 534config CGROUP_FREEZER 535 bool "Freezer cgroup subsystem" 536 depends on CGROUPS 537 help 538 Provides a way to freeze and unfreeze all tasks in a 539 cgroup. 540 541config CGROUP_DEVICE 542 bool "Device controller for cgroups" 543 depends on CGROUPS && EXPERIMENTAL 544 help 545 Provides a cgroup implementing whitelists for devices which 546 a process in the cgroup can mknod or open. 547 548config CPUSETS 549 bool "Cpuset support" 550 depends on CGROUPS 551 help 552 This option will let you create and manage CPUSETs which 553 allow dynamically partitioning a system into sets of CPUs and 554 Memory Nodes and assigning tasks to run only within those sets. 555 This is primarily useful on large SMP or NUMA systems. 556 557 Say N if unsure. 558 559config PROC_PID_CPUSET 560 bool "Include legacy /proc/<pid>/cpuset file" 561 depends on CPUSETS 562 default y 563 564config CGROUP_CPUACCT 565 bool "Simple CPU accounting cgroup subsystem" 566 depends on CGROUPS 567 help 568 Provides a simple Resource Controller for monitoring the 569 total CPU consumed by the tasks in a cgroup. 570 571config RESOURCE_COUNTERS 572 bool "Resource counters" 573 help 574 This option enables controller independent resource accounting 575 infrastructure that works with cgroups. 576 depends on CGROUPS 577 578config CGROUP_MEM_RES_CTLR 579 bool "Memory Resource Controller for Control Groups" 580 depends on CGROUPS && RESOURCE_COUNTERS 581 select MM_OWNER 582 help 583 Provides a memory resource controller that manages both anonymous 584 memory and page cache. (See Documentation/cgroups/memory.txt) 585 586 Note that setting this option increases fixed memory overhead 587 associated with each page of memory in the system. By this, 588 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 589 usage tracking struct at boot. Total amount of this is printed out 590 at boot. 591 592 Only enable when you're ok with these trade offs and really 593 sure you need the memory resource controller. Even when you enable 594 this, you can set "cgroup_disable=memory" at your boot option to 595 disable memory resource controller and you can avoid overheads. 596 (and lose benefits of memory resource controller) 597 598 This config option also selects MM_OWNER config option, which 599 could in turn add some fork/exit overhead. 600 601config CGROUP_MEM_RES_CTLR_SWAP 602 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)" 603 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL 604 help 605 Add swap management feature to memory resource controller. When you 606 enable this, you can limit mem+swap usage per cgroup. In other words, 607 when you disable this, memory resource controller has no cares to 608 usage of swap...a process can exhaust all of the swap. This extension 609 is useful when you want to avoid exhaustion swap but this itself 610 adds more overheads and consumes memory for remembering information. 611 Especially if you use 32bit system or small memory system, please 612 be careful about enabling this. When memory resource controller 613 is disabled by boot option, this will be automatically disabled and 614 there will be no overhead from this. Even when you set this config=y, 615 if boot option "noswapaccount" is set, swap will not be accounted. 616 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 617 size is 4096bytes, 512k per 1Gbytes of swap. 618 619endif # CGROUPS 620 621config MM_OWNER 622 bool 623 624config SYSFS_DEPRECATED 625 bool 626 627config SYSFS_DEPRECATED_V2 628 bool "enable deprecated sysfs features to support old userspace tools" 629 depends on SYSFS 630 default n 631 select SYSFS_DEPRECATED 632 help 633 This option switches the layout of sysfs to the deprecated 634 version. Do not use it on recent distributions. 635 636 The current sysfs layout features a unified device tree at 637 /sys/devices/, which is able to express a hierarchy between 638 class devices. If the deprecated option is set to Y, the 639 unified device tree is split into a bus device tree at 640 /sys/devices/ and several individual class device trees at 641 /sys/class/. The class and bus devices will be connected by 642 "<subsystem>:<name>" and the "device" links. The "block" 643 class devices, will not show up in /sys/class/block/. Some 644 subsystems will suppress the creation of some devices which 645 depend on the unified device tree. 646 647 This option is not a pure compatibility option that can 648 be safely enabled on newer distributions. It will change the 649 layout of sysfs to the non-extensible deprecated version, 650 and disable some features, which can not be exported without 651 confusing older userspace tools. Since 2007/2008 all major 652 distributions do not enable this option, and ship no tools which 653 depend on the deprecated layout or this option. 654 655 If you are using a new kernel on an older distribution, or use 656 older userspace tools, you might need to say Y here. Do not say Y, 657 if the original kernel, that came with your distribution, has 658 this option set to N. 659 660config RELAY 661 bool "Kernel->user space relay support (formerly relayfs)" 662 help 663 This option enables support for relay interface support in 664 certain file systems (such as debugfs). 665 It is designed to provide an efficient mechanism for tools and 666 facilities to relay large amounts of data from kernel space to 667 user space. 668 669 If unsure, say N. 670 671config NAMESPACES 672 bool "Namespaces support" if EMBEDDED 673 default !EMBEDDED 674 help 675 Provides the way to make tasks work with different objects using 676 the same id. For example same IPC id may refer to different objects 677 or same user id or pid may refer to different tasks when used in 678 different namespaces. 679 680config UTS_NS 681 bool "UTS namespace" 682 depends on NAMESPACES 683 help 684 In this namespace tasks see different info provided with the 685 uname() system call 686 687config IPC_NS 688 bool "IPC namespace" 689 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE) 690 help 691 In this namespace tasks work with IPC ids which correspond to 692 different IPC objects in different namespaces. 693 694config USER_NS 695 bool "User namespace (EXPERIMENTAL)" 696 depends on NAMESPACES && EXPERIMENTAL 697 help 698 This allows containers, i.e. vservers, to use user namespaces 699 to provide different user info for different servers. 700 If unsure, say N. 701 702config PID_NS 703 bool "PID Namespaces (EXPERIMENTAL)" 704 default n 705 depends on NAMESPACES && EXPERIMENTAL 706 help 707 Support process id namespaces. This allows having multiple 708 processes with the same pid as long as they are in different 709 pid namespaces. This is a building block of containers. 710 711 Unless you want to work with an experimental feature 712 say N here. 713 714config NET_NS 715 bool "Network namespace" 716 default n 717 depends on NAMESPACES && EXPERIMENTAL && NET 718 help 719 Allow user space to create what appear to be multiple instances 720 of the network stack. 721 722config BLK_DEV_INITRD 723 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 724 depends on BROKEN || !FRV 725 help 726 The initial RAM filesystem is a ramfs which is loaded by the 727 boot loader (loadlin or lilo) and that is mounted as root 728 before the normal boot procedure. It is typically used to 729 load modules needed to mount the "real" root file system, 730 etc. See <file:Documentation/initrd.txt> for details. 731 732 If RAM disk support (BLK_DEV_RAM) is also included, this 733 also enables initial RAM disk (initrd) support and adds 734 15 Kbytes (more on some other architectures) to the kernel size. 735 736 If unsure say Y. 737 738if BLK_DEV_INITRD 739 740source "usr/Kconfig" 741 742endif 743 744config CC_OPTIMIZE_FOR_SIZE 745 bool "Optimize for size" 746 default y 747 help 748 Enabling this option will pass "-Os" instead of "-O2" to gcc 749 resulting in a smaller kernel. 750 751 If unsure, say Y. 752 753config SYSCTL 754 bool 755 756config ANON_INODES 757 bool 758 759menuconfig EMBEDDED 760 bool "Configure standard kernel features (for small systems)" 761 help 762 This option allows certain base kernel options and settings 763 to be disabled or tweaked. This is for specialized 764 environments which can tolerate a "non-standard" kernel. 765 Only use this if you really know what you are doing. 766 767config UID16 768 bool "Enable 16-bit UID system calls" if EMBEDDED 769 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) 770 default y 771 help 772 This enables the legacy 16-bit UID syscall wrappers. 773 774config SYSCTL_SYSCALL 775 bool "Sysctl syscall support" if EMBEDDED 776 depends on PROC_SYSCTL 777 default y 778 select SYSCTL 779 ---help--- 780 sys_sysctl uses binary paths that have been found challenging 781 to properly maintain and use. The interface in /proc/sys 782 using paths with ascii names is now the primary path to this 783 information. 784 785 Almost nothing using the binary sysctl interface so if you are 786 trying to save some space it is probably safe to disable this, 787 making your kernel marginally smaller. 788 789 If unsure say Y here. 790 791config KALLSYMS 792 bool "Load all symbols for debugging/ksymoops" if EMBEDDED 793 default y 794 help 795 Say Y here to let the kernel print out symbolic crash information and 796 symbolic stack backtraces. This increases the size of the kernel 797 somewhat, as all symbols have to be loaded into the kernel image. 798 799config KALLSYMS_ALL 800 bool "Include all symbols in kallsyms" 801 depends on DEBUG_KERNEL && KALLSYMS 802 help 803 Normally kallsyms only contains the symbols of functions, for nicer 804 OOPS messages. Some debuggers can use kallsyms for other 805 symbols too: say Y here to include all symbols, if you need them 806 and you don't care about adding 300k to the size of your kernel. 807 808 Say N. 809 810config KALLSYMS_EXTRA_PASS 811 bool "Do an extra kallsyms pass" 812 depends on KALLSYMS 813 help 814 If kallsyms is not working correctly, the build will fail with 815 inconsistent kallsyms data. If that occurs, log a bug report and 816 turn on KALLSYMS_EXTRA_PASS which should result in a stable build. 817 Always say N here unless you find a bug in kallsyms, which must be 818 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while 819 you wait for kallsyms to be fixed. 820 821 822config HOTPLUG 823 bool "Support for hot-pluggable devices" if EMBEDDED 824 default y 825 help 826 This option is provided for the case where no hotplug or uevent 827 capabilities is wanted by the kernel. You should only consider 828 disabling this option for embedded systems that do not use modules, a 829 dynamic /dev tree, or dynamic device discovery. Just say Y. 830 831config PRINTK 832 default y 833 bool "Enable support for printk" if EMBEDDED 834 help 835 This option enables normal printk support. Removing it 836 eliminates most of the message strings from the kernel image 837 and makes the kernel more or less silent. As this makes it 838 very difficult to diagnose system problems, saying N here is 839 strongly discouraged. 840 841config BUG 842 bool "BUG() support" if EMBEDDED 843 default y 844 help 845 Disabling this option eliminates support for BUG and WARN, reducing 846 the size of your kernel image and potentially quietly ignoring 847 numerous fatal conditions. You should only consider disabling this 848 option for embedded systems with no facilities for reporting errors. 849 Just say Y. 850 851config ELF_CORE 852 default y 853 bool "Enable ELF core dumps" if EMBEDDED 854 help 855 Enable support for generating core dumps. Disabling saves about 4k. 856 857config PCSPKR_PLATFORM 858 bool "Enable PC-Speaker support" if EMBEDDED 859 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES 860 default y 861 help 862 This option allows to disable the internal PC-Speaker 863 support, saving some memory. 864 865config BASE_FULL 866 default y 867 bool "Enable full-sized data structures for core" if EMBEDDED 868 help 869 Disabling this option reduces the size of miscellaneous core 870 kernel data structures. This saves memory on small machines, 871 but may reduce performance. 872 873config FUTEX 874 bool "Enable futex support" if EMBEDDED 875 default y 876 select RT_MUTEXES 877 help 878 Disabling this option will cause the kernel to be built without 879 support for "fast userspace mutexes". The resulting kernel may not 880 run glibc-based applications correctly. 881 882config EPOLL 883 bool "Enable eventpoll support" if EMBEDDED 884 default y 885 select ANON_INODES 886 help 887 Disabling this option will cause the kernel to be built without 888 support for epoll family of system calls. 889 890config SIGNALFD 891 bool "Enable signalfd() system call" if EMBEDDED 892 select ANON_INODES 893 default y 894 help 895 Enable the signalfd() system call that allows to receive signals 896 on a file descriptor. 897 898 If unsure, say Y. 899 900config TIMERFD 901 bool "Enable timerfd() system call" if EMBEDDED 902 select ANON_INODES 903 default y 904 help 905 Enable the timerfd() system call that allows to receive timer 906 events on a file descriptor. 907 908 If unsure, say Y. 909 910config EVENTFD 911 bool "Enable eventfd() system call" if EMBEDDED 912 select ANON_INODES 913 default y 914 help 915 Enable the eventfd() system call that allows to receive both 916 kernel notification (ie. KAIO) or userspace notifications. 917 918 If unsure, say Y. 919 920config SHMEM 921 bool "Use full shmem filesystem" if EMBEDDED 922 default y 923 depends on MMU 924 help 925 The shmem is an internal filesystem used to manage shared memory. 926 It is backed by swap and manages resource limits. It is also exported 927 to userspace as tmpfs if TMPFS is enabled. Disabling this 928 option replaces shmem and tmpfs with the much simpler ramfs code, 929 which may be appropriate on small systems without swap. 930 931config AIO 932 bool "Enable AIO support" if EMBEDDED 933 default y 934 help 935 This option enables POSIX asynchronous I/O which may by used 936 by some high performance threaded applications. Disabling 937 this option saves about 7k. 938 939config HAVE_PERF_EVENTS 940 bool 941 help 942 See tools/perf/design.txt for details. 943 944config PERF_USE_VMALLOC 945 bool 946 help 947 See tools/perf/design.txt for details 948 949menu "Kernel Performance Events And Counters" 950 951config PERF_EVENTS 952 bool "Kernel performance events and counters" 953 default y if (PROFILING || PERF_COUNTERS) 954 depends on HAVE_PERF_EVENTS 955 select ANON_INODES 956 help 957 Enable kernel support for various performance events provided 958 by software and hardware. 959 960 Software events are supported either built-in or via the 961 use of generic tracepoints. 962 963 Most modern CPUs support performance events via performance 964 counter registers. These registers count the number of certain 965 types of hw events: such as instructions executed, cachemisses 966 suffered, or branches mis-predicted - without slowing down the 967 kernel or applications. These registers can also trigger interrupts 968 when a threshold number of events have passed - and can thus be 969 used to profile the code that runs on that CPU. 970 971 The Linux Performance Event subsystem provides an abstraction of 972 these software and hardware event capabilities, available via a 973 system call and used by the "perf" utility in tools/perf/. It 974 provides per task and per CPU counters, and it provides event 975 capabilities on top of those. 976 977 Say Y if unsure. 978 979config EVENT_PROFILE 980 bool "Tracepoint profiling sources" 981 depends on PERF_EVENTS && EVENT_TRACING 982 default y 983 help 984 Allow the use of tracepoints as software performance events. 985 986 When this is enabled, you can create perf events based on 987 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID 988 found in debugfs://tracing/events/*/*/id. (The -e/--events 989 option to the perf tool can parse and interpret symbolic 990 tracepoints, in the subsystem:tracepoint_name format.) 991 992config PERF_COUNTERS 993 bool "Kernel performance counters (old config option)" 994 depends on HAVE_PERF_EVENTS 995 help 996 This config has been obsoleted by the PERF_EVENTS 997 config option - please see that one for details. 998 999 It has no effect on the kernel whether you enable 1000 it or not, it is a compatibility placeholder.
1001 1002 Say N if unsure. 1003 1004config DEBUG_PERF_USE_VMALLOC 1005 default n 1006 bool "Debug: use vmalloc to back perf mmap() buffers" 1007 depends on PERF_EVENTS && DEBUG_KERNEL 1008 select PERF_USE_VMALLOC 1009 help 1010 Use vmalloc memory to back perf mmap() buffers. 1011 1012 Mostly useful for debugging the vmalloc code on platforms 1013 that don't require it. 1014 1015 Say N if unsure. 1016 1017endmenu 1018 1019config VM_EVENT_COUNTERS 1020 default y 1021 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED 1022 help 1023 VM event counters are needed for event counts to be shown. 1024 This option allows the disabling of the VM event counters 1025 on EMBEDDED systems. /proc/vmstat will only show page counts 1026 if VM event counters are disabled. 1027 1028config PCI_QUIRKS 1029 default y 1030 bool "Enable PCI quirk workarounds" if EMBEDDED 1031 depends on PCI 1032 help 1033 This enables workarounds for various PCI chipset 1034 bugs/quirks. Disable this only if your target machine is 1035 unaffected by PCI quirks. 1036 1037config SLUB_DEBUG 1038 default y 1039 bool "Enable SLUB debugging support" if EMBEDDED 1040 depends on SLUB && SYSFS 1041 help 1042 SLUB has extensive debug support features. Disabling these can 1043 result in significant savings in code size. This also disables 1044 SLUB sysfs support. /sys/slab will not exist and there will be 1045 no support for cache validation etc. 1046 1047config COMPAT_BRK 1048 bool "Disable heap randomization" 1049 default y 1050 help 1051 Randomizing heap placement makes heap exploits harder, but it 1052 also breaks ancient binaries (including anything libc5 based). 1053 This option changes the bootup default to heap randomization 1054 disabled, and can be overridden at runtime by setting 1055 /proc/sys/kernel/randomize_va_space to 2. 1056 1057 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1058 1059choice 1060 prompt "Choose SLAB allocator" 1061 default SLUB 1062 help 1063 This option allows to select a slab allocator. 1064 1065config SLAB 1066 bool "SLAB" 1067 help 1068 The regular slab allocator that is established and known to work 1069 well in all environments. It organizes cache hot objects in 1070 per cpu and per node queues. 1071 1072config SLUB 1073 bool "SLUB (Unqueued Allocator)" 1074 help 1075 SLUB is a slab allocator that minimizes cache line usage 1076 instead of managing queues of cached objects (SLAB approach). 1077 Per cpu caching is realized using slabs of objects instead 1078 of queues of objects. SLUB can use memory efficiently 1079 and has enhanced diagnostics. SLUB is the default choice for 1080 a slab allocator. 1081 1082config SLOB 1083 depends on EMBEDDED 1084 bool "SLOB (Simple Allocator)" 1085 help 1086 SLOB replaces the stock allocator with a drastically simpler 1087 allocator. SLOB is generally more space efficient but 1088 does not perform as well on large systems. 1089 1090endchoice 1091 1092config MMAP_ALLOW_UNINITIALIZED 1093 bool "Allow mmapped anonymous memory to be uninitialized" 1094 depends on EMBEDDED && !MMU 1095 default n 1096 help 1097 Normally, and according to the Linux spec, anonymous memory obtained 1098 from mmap() has it's contents cleared before it is passed to 1099 userspace. Enabling this config option allows you to request that 1100 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1101 providing a huge performance boost. If this option is not enabled, 1102 then the flag will be ignored. 1103 1104 This is taken advantage of by uClibc's malloc(), and also by 1105 ELF-FDPIC binfmt's brk and stack allocator. 1106 1107 Because of the obvious security issues, this option should only be 1108 enabled on embedded devices where you control what is run in 1109 userspace. Since that isn't generally a problem on no-MMU systems, 1110 it is normally safe to say Y here. 1111 1112 See Documentation/nommu-mmap.txt for more information. 1113 1114config PROFILING 1115 bool "Profiling support (EXPERIMENTAL)" 1116 help 1117 Say Y here to enable the extended profiling support mechanisms used 1118 by profilers such as OProfile. 1119 1120# 1121# Place an empty function call at each tracepoint site. Can be 1122# dynamically changed for a probe function. 1123# 1124config TRACEPOINTS 1125 bool 1126 1127source "arch/Kconfig" 1128 1129config SLOW_WORK 1130 default n 1131 bool 1132 help 1133 The slow work thread pool provides a number of dynamically allocated 1134 threads that can be used by the kernel to perform operations that 1135 take a relatively long time. 1136 1137 An example of this would be CacheFiles doing a path lookup followed 1138 by a series of mkdirs and a create call, all of which have to touch 1139 disk. 1140 1141 See Documentation/slow-work.txt. 1142 1143config SLOW_WORK_DEBUG 1144 bool "Slow work debugging through debugfs" 1145 default n 1146 depends on SLOW_WORK && DEBUG_FS 1147 help 1148 Display the contents of the slow work run queue through debugfs, 1149 including items currently executing. 1150 1151 See Documentation/slow-work.txt. 1152 1153endmenu # General setup 1154 1155config HAVE_GENERIC_DMA_COHERENT 1156 bool 1157 default n 1158 1159config SLABINFO 1160 bool 1161 depends on PROC_FS 1162 depends on SLAB || SLUB_DEBUG 1163 default y 1164 1165config RT_MUTEXES 1166 boolean 1167 1168config BASE_SMALL 1169 int 1170 default 0 if BASE_FULL 1171 default 1 if !BASE_FULL 1172 1173menuconfig MODULES 1174 bool "Enable loadable module support" 1175 help 1176 Kernel modules are small pieces of compiled code which can 1177 be inserted in the running kernel, rather than being 1178 permanently built into the kernel. You use the "modprobe" 1179 tool to add (and sometimes remove) them. If you say Y here, 1180 many parts of the kernel can be built as modules (by 1181 answering M instead of Y where indicated): this is most 1182 useful for infrequently used options which are not required 1183 for booting. For more information, see the man pages for 1184 modprobe, lsmod, modinfo, insmod and rmmod. 1185 1186 If you say Y here, you will need to run "make 1187 modules_install" to put the modules under /lib/modules/ 1188 where modprobe can find them (you may need to be root to do 1189 this). 1190 1191 If unsure, say Y. 1192 1193if MODULES 1194 1195config MODULE_FORCE_LOAD 1196 bool "Forced module loading" 1197 default n 1198 help 1199 Allow loading of modules without version information (ie. modprobe 1200 --force). Forced module loading sets the 'F' (forced) taint flag and 1201 is usually a really bad idea. 1202 1203config MODULE_UNLOAD 1204 bool "Module unloading" 1205 help 1206 Without this option you will not be able to unload any 1207 modules (note that some modules may not be unloadable 1208 anyway), which makes your kernel smaller, faster 1209 and simpler. If unsure, say Y. 1210 1211config MODULE_FORCE_UNLOAD 1212 bool "Forced module unloading" 1213 depends on MODULE_UNLOAD && EXPERIMENTAL 1214 help 1215 This option allows you to force a module to unload, even if the 1216 kernel believes it is unsafe: the kernel will remove the module 1217 without waiting for anyone to stop using it (using the -f option to 1218 rmmod). This is mainly for kernel developers and desperate users. 1219 If unsure, say N. 1220 1221config MODVERSIONS 1222 bool "Module versioning support" 1223 help 1224 Usually, you have to use modules compiled with your kernel. 1225 Saying Y here makes it sometimes possible to use modules 1226 compiled for different kernels, by adding enough information 1227 to the modules to (hopefully) spot any changes which would 1228 make them incompatible with the kernel you are running. If 1229 unsure, say N. 1230 1231config MODULE_SRCVERSION_ALL 1232 bool "Source checksum for all modules" 1233 help 1234 Modules which contain a MODULE_VERSION get an extra "srcversion" 1235 field inserted into their modinfo section, which contains a 1236 sum of the source files which made it. This helps maintainers 1237 see exactly which source was used to build a module (since 1238 others sometimes change the module source without updating 1239 the version). With this option, such a "srcversion" field 1240 will be created for all modules. If unsure, say N. 1241 1242endif # MODULES 1243 1244config INIT_ALL_POSSIBLE 1245 bool 1246 help 1247 Back when each arch used to define their own cpu_online_map and 1248 cpu_possible_map, some of them chose to initialize cpu_possible_map 1249 with all 1s, and others with all 0s. When they were centralised, 1250 it was better to provide this option than to break all the archs 1251 and have several arch maintainers pursuing me down dark alleys. 1252 1253config STOP_MACHINE 1254 bool 1255 default y 1256 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1257 help 1258 Need stop_machine() primitive. 1259 1260source "block/Kconfig" 1261 1262config PREEMPT_NOTIFIERS 1263 bool 1264 1265source "kernel/Kconfig.locks" 1266