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 24config HAVE_IRQ_WORK 25 bool 26 27config IRQ_WORK 28 bool 29 depends on HAVE_IRQ_WORK 30 31menu "General setup" 32 33config EXPERIMENTAL 34 bool "Prompt for development and/or incomplete code/drivers" 35 ---help--- 36 Some of the various things that Linux supports (such as network 37 drivers, file systems, network protocols, etc.) can be in a state 38 of development where the functionality, stability, or the level of 39 testing is not yet high enough for general use. This is usually 40 known as the "alpha-test" phase among developers. If a feature is 41 currently in alpha-test, then the developers usually discourage 42 uninformed widespread use of this feature by the general public to 43 avoid "Why doesn't this work?" type mail messages. However, active 44 testing and use of these systems is welcomed. Just be aware that it 45 may not meet the normal level of reliability or it may fail to work 46 in some special cases. Detailed bug reports from people familiar 47 with the kernel internals are usually welcomed by the developers 48 (before submitting bug reports, please read the documents 49 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 50 <file:Documentation/BUG-HUNTING>, and 51 <file:Documentation/oops-tracing.txt> in the kernel source). 52 53 This option will also make obsoleted drivers available. These are 54 drivers that have been replaced by something else, and/or are 55 scheduled to be removed in a future kernel release. 56 57 Unless you intend to help test and develop a feature or driver that 58 falls into this category, or you have a situation that requires 59 using these features, you should probably say N here, which will 60 cause the configurator to present you with fewer choices. If 61 you say Y here, you will be offered the choice of using features or 62 drivers that are currently considered to be in the alpha-test phase. 63 64config BROKEN 65 bool 66 67config BROKEN_ON_SMP 68 bool 69 depends on BROKEN || !SMP 70 default y 71 72config LOCK_KERNEL 73 bool 74 depends on (SMP || PREEMPT) && BKL 75 default y 76 77config INIT_ENV_ARG_LIMIT 78 int 79 default 32 if !UML 80 default 128 if UML 81 help 82 Maximum of each of the number of arguments and environment 83 variables passed to init from the kernel command line. 84 85 86config CROSS_COMPILE 87 string "Cross-compiler tool prefix" 88 help 89 Same as running 'make CROSS_COMPILE=prefix-' but stored for 90 default make runs in this kernel build directory. You don't 91 need to set this unless you want the configured kernel build 92 directory to select the cross-compiler automatically. 93 94config LOCALVERSION 95 string "Local version - append to kernel release" 96 help 97 Append an extra string to the end of your kernel version. 98 This will show up when you type uname, for example. 99 The string you set here will be appended after the contents of 100 any files with a filename matching localversion* in your 101 object and source tree, in that order. Your total string can 102 be a maximum of 64 characters. 103 104config LOCALVERSION_AUTO 105 bool "Automatically append version information to the version string" 106 default y 107 help 108 This will try to automatically determine if the current tree is a 109 release tree by looking for git tags that belong to the current 110 top of tree revision. 111 112 A string of the format -gxxxxxxxx will be added to the localversion 113 if a git-based tree is found. The string generated by this will be 114 appended after any matching localversion* files, and after the value 115 set in CONFIG_LOCALVERSION. 116 117 (The actual string used here is the first eight characters produced 118 by running the command: 119 120 $ git rev-parse --verify HEAD 121 122 which is done within the script "scripts/setlocalversion".) 123 124config HAVE_KERNEL_GZIP 125 bool 126 127config HAVE_KERNEL_BZIP2 128 bool 129 130config HAVE_KERNEL_LZMA 131 bool 132 133config HAVE_KERNEL_XZ 134 bool 135 136config HAVE_KERNEL_LZO 137 bool 138 139choice 140 prompt "Kernel compression mode" 141 default KERNEL_GZIP 142 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 143 help 144 The linux kernel is a kind of self-extracting executable. 145 Several compression algorithms are available, which differ 146 in efficiency, compression and decompression speed. 147 Compression speed is only relevant when building a kernel. 148 Decompression speed is relevant at each boot. 149 150 If you have any problems with bzip2 or lzma compressed 151 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 152 version of this functionality (bzip2 only), for 2.4, was 153 supplied by Christian Ludwig) 154 155 High compression options are mostly useful for users, who 156 are low on disk space (embedded systems), but for whom ram 157 size matters less. 158 159 If in doubt, select 'gzip' 160 161config KERNEL_GZIP 162 bool "Gzip" 163 depends on HAVE_KERNEL_GZIP 164 help 165 The old and tried gzip compression. It provides a good balance 166 between compression ratio and decompression speed. 167 168config KERNEL_BZIP2 169 bool "Bzip2" 170 depends on HAVE_KERNEL_BZIP2 171 help 172 Its compression ratio and speed is intermediate. 173 Decompression speed is slowest among the three. The kernel 174 size is about 10% smaller with bzip2, in comparison to gzip. 175 Bzip2 uses a large amount of memory. For modern kernels you 176 will need at least 8MB RAM or more for booting. 177 178config KERNEL_LZMA 179 bool "LZMA" 180 depends on HAVE_KERNEL_LZMA 181 help 182 The most recent compression algorithm. 183 Its ratio is best, decompression speed is between the other 184 two. Compression is slowest. The kernel size is about 33% 185 smaller with LZMA in comparison to gzip. 186 187config KERNEL_XZ 188 bool "XZ" 189 depends on HAVE_KERNEL_XZ 190 help 191 XZ uses the LZMA2 algorithm and instruction set specific 192 BCJ filters which can improve compression ratio of executable 193 code. The size of the kernel is about 30% smaller with XZ in 194 comparison to gzip. On architectures for which there is a BCJ 195 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 196 will create a few percent smaller kernel than plain LZMA. 197 198 The speed is about the same as with LZMA: The decompression 199 speed of XZ is better than that of bzip2 but worse than gzip 200 and LZO. Compression is slow. 201 202config KERNEL_LZO 203 bool "LZO" 204 depends on HAVE_KERNEL_LZO 205 help 206 Its compression ratio is the poorest among the 4. The kernel 207 size is about 10% bigger than gzip; however its speed 208 (both compression and decompression) is the fastest. 209 210endchoice 211 212config SWAP 213 bool "Support for paging of anonymous memory (swap)" 214 depends on MMU && BLOCK 215 default y 216 help 217 This option allows you to choose whether you want to have support 218 for so called swap devices or swap files in your kernel that are 219 used to provide more virtual memory than the actual RAM present 220 in your computer. If unsure say Y. 221 222config SYSVIPC 223 bool "System V IPC" 224 ---help--- 225 Inter Process Communication is a suite of library functions and 226 system calls which let processes (running programs) synchronize and 227 exchange information. It is generally considered to be a good thing, 228 and some programs won't run unless you say Y here. In particular, if 229 you want to run the DOS emulator dosemu under Linux (read the 230 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 231 you'll need to say Y here. 232 233 You can find documentation about IPC with "info ipc" and also in 234 section 6.4 of the Linux Programmer's Guide, available from 235 <http://www.tldp.org/guides.html>. 236 237config SYSVIPC_SYSCTL 238 bool 239 depends on SYSVIPC 240 depends on SYSCTL 241 default y 242 243config POSIX_MQUEUE 244 bool "POSIX Message Queues" 245 depends on NET && EXPERIMENTAL 246 ---help--- 247 POSIX variant of message queues is a part of IPC. In POSIX message 248 queues every message has a priority which decides about succession 249 of receiving it by a process. If you want to compile and run 250 programs written e.g. for Solaris with use of its POSIX message 251 queues (functions mq_*) say Y here. 252 253 POSIX message queues are visible as a filesystem called 'mqueue' 254 and can be mounted somewhere if you want to do filesystem 255 operations on message queues. 256 257 If unsure, say Y. 258 259config POSIX_MQUEUE_SYSCTL 260 bool 261 depends on POSIX_MQUEUE 262 depends on SYSCTL 263 default y 264 265config BSD_PROCESS_ACCT 266 bool "BSD Process Accounting" 267 help 268 If you say Y here, a user level program will be able to instruct the 269 kernel (via a special system call) to write process accounting 270 information to a file: whenever a process exits, information about 271 that process will be appended to the file by the kernel. The 272 information includes things such as creation time, owning user, 273 command name, memory usage, controlling terminal etc. (the complete 274 list is in the struct acct in <file:include/linux/acct.h>). It is 275 up to the user level program to do useful things with this 276 information. This is generally a good idea, so say Y. 277 278config BSD_PROCESS_ACCT_V3 279 bool "BSD Process Accounting version 3 file format" 280 depends on BSD_PROCESS_ACCT 281 default n 282 help 283 If you say Y here, the process accounting information is written 284 in a new file format that also logs the process IDs of each 285 process and it's parent. Note that this file format is incompatible 286 with previous v0/v1/v2 file formats, so you will need updated tools 287 for processing it. A preliminary version of these tools is available 288 at <http://www.gnu.org/software/acct/>. 289 290config TASKSTATS 291 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 292 depends on NET 293 default n 294 help 295 Export selected statistics for tasks/processes through the 296 generic netlink interface. Unlike BSD process accounting, the 297 statistics are available during the lifetime of tasks/processes as 298 responses to commands. Like BSD accounting, they are sent to user 299 space on task exit. 300 301 Say N if unsure. 302 303config TASK_DELAY_ACCT 304 bool "Enable per-task delay accounting (EXPERIMENTAL)" 305 depends on TASKSTATS 306 help 307 Collect information on time spent by a task waiting for system 308 resources like cpu, synchronous block I/O completion and swapping 309 in pages. Such statistics can help in setting a task's priorities 310 relative to other tasks for cpu, io, rss limits etc. 311 312 Say N if unsure. 313 314config TASK_XACCT 315 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 316 depends on TASKSTATS 317 help 318 Collect extended task accounting data and send the data 319 to userland for processing over the taskstats interface. 320 321 Say N if unsure. 322 323config TASK_IO_ACCOUNTING 324 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 325 depends on TASK_XACCT 326 help 327 Collect information on the number of bytes of storage I/O which this 328 task has caused. 329 330 Say N if unsure. 331 332config AUDIT 333 bool "Auditing support" 334 depends on NET 335 help 336 Enable auditing infrastructure that can be used with another 337 kernel subsystem, such as SELinux (which requires this for 338 logging of avc messages output). Does not do system-call 339 auditing without CONFIG_AUDITSYSCALL. 340 341config AUDITSYSCALL 342 bool "Enable system-call auditing support" 343 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH) 344 default y if SECURITY_SELINUX 345 help 346 Enable low-overhead system-call auditing infrastructure that 347 can be used independently or with another kernel subsystem, 348 such as SELinux. 349 350config AUDIT_WATCH 351 def_bool y 352 depends on AUDITSYSCALL 353 select FSNOTIFY 354 355config AUDIT_TREE 356 def_bool y 357 depends on AUDITSYSCALL 358 select FSNOTIFY 359 360source "kernel/irq/Kconfig" 361 362menu "RCU Subsystem" 363 364choice 365 prompt "RCU Implementation" 366 default TREE_RCU 367 368config TREE_RCU 369 bool "Tree-based hierarchical RCU" 370 depends on !PREEMPT && SMP 371 help 372 This option selects the RCU implementation that is 373 designed for very large SMP system with hundreds or 374 thousands of CPUs. It also scales down nicely to 375 smaller systems. 376 377config TREE_PREEMPT_RCU 378 bool "Preemptible tree-based hierarchical RCU" 379 depends on PREEMPT 380 help 381 This option selects the RCU implementation that is 382 designed for very large SMP systems with hundreds or 383 thousands of CPUs, but for which real-time response 384 is also required. It also scales down nicely to 385 smaller systems. 386 387config TINY_RCU 388 bool "UP-only small-memory-footprint RCU" 389 depends on !SMP 390 help 391 This option selects the RCU implementation that is 392 designed for UP systems from which real-time response 393 is not required. This option greatly reduces the 394 memory footprint of RCU. 395 396config TINY_PREEMPT_RCU 397 bool "Preemptible UP-only small-memory-footprint RCU" 398 depends on !SMP && PREEMPT 399 help 400 This option selects the RCU implementation that is designed 401 for real-time UP systems. This option greatly reduces the 402 memory footprint of RCU. 403 404endchoice 405 406config PREEMPT_RCU 407 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 408 help 409 This option enables preemptible-RCU code that is common between 410 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 411 412config RCU_TRACE 413 bool "Enable tracing for RCU" 414 help 415 This option provides tracing in RCU which presents stats 416 in debugfs for debugging RCU implementation. 417 418 Say Y here if you want to enable RCU tracing 419 Say N if you are unsure. 420 421config RCU_FANOUT 422 int "Tree-based hierarchical RCU fanout value" 423 range 2 64 if 64BIT 424 range 2 32 if !64BIT 425 depends on TREE_RCU || TREE_PREEMPT_RCU 426 default 64 if 64BIT 427 default 32 if !64BIT 428 help 429 This option controls the fanout of hierarchical implementations 430 of RCU, allowing RCU to work efficiently on machines with 431 large numbers of CPUs. This value must be at least the fourth 432 root of NR_CPUS, which allows NR_CPUS to be insanely large. 433 The default value of RCU_FANOUT should be used for production 434 systems, but if you are stress-testing the RCU implementation 435 itself, small RCU_FANOUT values allow you to test large-system 436 code paths on small(er) systems. 437 438 Select a specific number if testing RCU itself. 439 Take the default if unsure. 440 441config RCU_FANOUT_EXACT 442 bool "Disable tree-based hierarchical RCU auto-balancing" 443 depends on TREE_RCU || TREE_PREEMPT_RCU 444 default n 445 help 446 This option forces use of the exact RCU_FANOUT value specified, 447 regardless of imbalances in the hierarchy. This is useful for 448 testing RCU itself, and might one day be useful on systems with 449 strong NUMA behavior. 450 451 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 452 453 Say N if unsure. 454 455config RCU_FAST_NO_HZ 456 bool "Accelerate last non-dyntick-idle CPU's grace periods" 457 depends on TREE_RCU && NO_HZ && SMP 458 default n 459 help 460 This option causes RCU to attempt to accelerate grace periods 461 in order to allow the final CPU to enter dynticks-idle state 462 more quickly. On the other hand, this option increases the 463 overhead of the dynticks-idle checking, particularly on systems 464 with large numbers of CPUs. 465 466 Say Y if energy efficiency is critically important, particularly 467 if you have relatively few CPUs. 468 469 Say N if you are unsure. 470 471config TREE_RCU_TRACE 472 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 473 select DEBUG_FS 474 help 475 This option provides tracing for the TREE_RCU and 476 TREE_PREEMPT_RCU implementations, permitting Makefile to 477 trivially select kernel/rcutree_trace.c. 478 479config RCU_BOOST 480 bool "Enable RCU priority boosting" 481 depends on RT_MUTEXES && TINY_PREEMPT_RCU 482 default n 483 help 484 This option boosts the priority of preempted RCU readers that 485 block the current preemptible RCU grace period for too long. 486 This option also prevents heavy loads from blocking RCU 487 callback invocation for all flavors of RCU. 488 489 Say Y here if you are working with real-time apps or heavy loads 490 Say N here if you are unsure. 491 492config RCU_BOOST_PRIO 493 int "Real-time priority to boost RCU readers to" 494 range 1 99 495 depends on RCU_BOOST 496 default 1 497 help 498 This option specifies the real-time priority to which preempted 499 RCU readers are to be boosted. If you are working with CPU-bound 500 real-time applications, you should specify a priority higher then 501 the highest-priority CPU-bound application. 502 503 Specify the real-time priority, or take the default if unsure. 504 505config RCU_BOOST_DELAY 506 int "Milliseconds to delay boosting after RCU grace-period start" 507 range 0 3000 508 depends on RCU_BOOST 509 default 500 510 help 511 This option specifies the time to wait after the beginning of 512 a given grace period before priority-boosting preempted RCU 513 readers blocking that grace period. Note that any RCU reader 514 blocking an expedited RCU grace period is boosted immediately. 515 516 Accept the default if unsure. 517 518endmenu # "RCU Subsystem" 519 520config IKCONFIG 521 tristate "Kernel .config support" 522 ---help--- 523 This option enables the complete Linux kernel ".config" file 524 contents to be saved in the kernel. It provides documentation 525 of which kernel options are used in a running kernel or in an 526 on-disk kernel. This information can be extracted from the kernel 527 image file with the script scripts/extract-ikconfig and used as 528 input to rebuild the current kernel or to build another kernel. 529 It can also be extracted from a running kernel by reading 530 /proc/config.gz if enabled (below). 531 532config IKCONFIG_PROC 533 bool "Enable access to .config through /proc/config.gz" 534 depends on IKCONFIG && PROC_FS 535 ---help--- 536 This option enables access to the kernel configuration file 537 through /proc/config.gz. 538 539config LOG_BUF_SHIFT 540 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 541 range 12 21 542 default 17 543 help 544 Select kernel log buffer size as a power of 2. 545 Examples: 546 17 => 128 KB 547 16 => 64 KB 548 15 => 32 KB 549 14 => 16 KB 550 13 => 8 KB 551 12 => 4 KB 552 553# 554# Architectures with an unreliable sched_clock() should select this: 555# 556config HAVE_UNSTABLE_SCHED_CLOCK 557 bool 558 559menuconfig CGROUPS 560 boolean "Control Group support" 561 depends on EVENTFD 562 help 563 This option adds support for grouping sets of processes together, for 564 use with process control subsystems such as Cpusets, CFS, memory 565 controls or device isolation. 566 See 567 - Documentation/scheduler/sched-design-CFS.txt (CFS) 568 - Documentation/cgroups/ (features for grouping, isolation 569 and resource control) 570 571 Say N if unsure. 572 573if CGROUPS 574 575config CGROUP_DEBUG 576 bool "Example debug cgroup subsystem" 577 default n 578 help 579 This option enables a simple cgroup subsystem that 580 exports useful debugging information about the cgroups 581 framework. 582 583 Say N if unsure. 584 585config CGROUP_NS 586 bool "Namespace cgroup subsystem" 587 help 588 Provides a simple namespace cgroup subsystem to 589 provide hierarchical naming of sets of namespaces, 590 for instance virtual servers and checkpoint/restart 591 jobs. 592 593config CGROUP_FREEZER 594 bool "Freezer cgroup subsystem" 595 help 596 Provides a way to freeze and unfreeze all tasks in a 597 cgroup. 598 599config CGROUP_DEVICE 600 bool "Device controller for cgroups" 601 help 602 Provides a cgroup implementing whitelists for devices which 603 a process in the cgroup can mknod or open. 604 605config CPUSETS 606 bool "Cpuset support" 607 help 608 This option will let you create and manage CPUSETs which 609 allow dynamically partitioning a system into sets of CPUs and 610 Memory Nodes and assigning tasks to run only within those sets. 611 This is primarily useful on large SMP or NUMA systems. 612 613 Say N if unsure. 614 615config PROC_PID_CPUSET 616 bool "Include legacy /proc/<pid>/cpuset file" 617 depends on CPUSETS 618 default y 619 620config CGROUP_CPUACCT 621 bool "Simple CPU accounting cgroup subsystem" 622 help 623 Provides a simple Resource Controller for monitoring the 624 total CPU consumed by the tasks in a cgroup. 625 626config RESOURCE_COUNTERS 627 bool "Resource counters" 628 help 629 This option enables controller independent resource accounting 630 infrastructure that works with cgroups. 631 632config CGROUP_MEM_RES_CTLR 633 bool "Memory Resource Controller for Control Groups" 634 depends on RESOURCE_COUNTERS 635 select MM_OWNER 636 help 637 Provides a memory resource controller that manages both anonymous 638 memory and page cache. (See Documentation/cgroups/memory.txt) 639 640 Note that setting this option increases fixed memory overhead 641 associated with each page of memory in the system. By this, 642 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 643 usage tracking struct at boot. Total amount of this is printed out 644 at boot. 645 646 Only enable when you're ok with these trade offs and really 647 sure you need the memory resource controller. Even when you enable 648 this, you can set "cgroup_disable=memory" at your boot option to 649 disable memory resource controller and you can avoid overheads. 650 (and lose benefits of memory resource controller) 651 652 This config option also selects MM_OWNER config option, which 653 could in turn add some fork/exit overhead. 654 655config CGROUP_MEM_RES_CTLR_SWAP 656 bool "Memory Resource Controller Swap Extension" 657 depends on CGROUP_MEM_RES_CTLR && SWAP 658 help 659 Add swap management feature to memory resource controller. When you 660 enable this, you can limit mem+swap usage per cgroup. In other words, 661 when you disable this, memory resource controller has no cares to 662 usage of swap...a process can exhaust all of the swap. This extension 663 is useful when you want to avoid exhaustion swap but this itself 664 adds more overheads and consumes memory for remembering information. 665 Especially if you use 32bit system or small memory system, please 666 be careful about enabling this. When memory resource controller 667 is disabled by boot option, this will be automatically disabled and 668 there will be no overhead from this. Even when you set this config=y, 669 if boot option "noswapaccount" is set, swap will not be accounted. 670 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 671 size is 4096bytes, 512k per 1Gbytes of swap. 672config CGROUP_MEM_RES_CTLR_SWAP_ENABLED 673 bool "Memory Resource Controller Swap Extension enabled by default" 674 depends on CGROUP_MEM_RES_CTLR_SWAP 675 default y 676 help 677 Memory Resource Controller Swap Extension comes with its price in 678 a bigger memory consumption. General purpose distribution kernels 679 which want to enable the feature but keep it disabled by default 680 and let the user enable it by swapaccount boot command line 681 parameter should have this option unselected. 682 For those who want to have the feature enabled by default should 683 select this option (if, for some reason, they need to disable it 684 then noswapaccount does the trick). 685 686menuconfig CGROUP_SCHED 687 bool "Group CPU scheduler" 688 depends on EXPERIMENTAL 689 default n 690 help 691 This feature lets CPU scheduler recognize task groups and control CPU 692 bandwidth allocation to such task groups. It uses cgroups to group 693 tasks. 694 695if CGROUP_SCHED 696config FAIR_GROUP_SCHED 697 bool "Group scheduling for SCHED_OTHER" 698 depends on CGROUP_SCHED 699 default CGROUP_SCHED 700 701config RT_GROUP_SCHED 702 bool "Group scheduling for SCHED_RR/FIFO" 703 depends on EXPERIMENTAL 704 depends on CGROUP_SCHED 705 default n 706 help 707 This feature lets you explicitly allocate real CPU bandwidth 708 to task groups. If enabled, it will also make it impossible to 709 schedule realtime tasks for non-root users until you allocate 710 realtime bandwidth for them. 711 See Documentation/scheduler/sched-rt-group.txt for more information. 712 713endif #CGROUP_SCHED 714 715config BLK_CGROUP 716 tristate "Block IO controller" 717 depends on BLOCK 718 default n 719 ---help--- 720 Generic block IO controller cgroup interface. This is the common 721 cgroup interface which should be used by various IO controlling 722 policies. 723 724 Currently, CFQ IO scheduler uses it to recognize task groups and 725 control disk bandwidth allocation (proportional time slice allocation) 726 to such task groups. It is also used by bio throttling logic in 727 block layer to implement upper limit in IO rates on a device. 728 729 This option only enables generic Block IO controller infrastructure. 730 One needs to also enable actual IO controlling logic/policy. For 731 enabling proportional weight division of disk bandwidth in CFQ seti 732 CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set 733 CONFIG_BLK_THROTTLE=y. 734 735 See Documentation/cgroups/blkio-controller.txt for more information. 736 737config DEBUG_BLK_CGROUP 738 bool "Enable Block IO controller debugging" 739 depends on BLK_CGROUP 740 default n 741 ---help--- 742 Enable some debugging help. Currently it exports additional stat 743 files in a cgroup which can be useful for debugging. 744 745endif # CGROUPS 746 747menuconfig NAMESPACES 748 bool "Namespaces support" if EXPERT 749 default !EXPERT 750 help 751 Provides the way to make tasks work with different objects using 752 the same id. For example same IPC id may refer to different objects 753 or same user id or pid may refer to different tasks when used in 754 different namespaces. 755 756if NAMESPACES 757 758config UTS_NS 759 bool "UTS namespace" 760 default y 761 help 762 In this namespace tasks see different info provided with the 763 uname() system call 764 765config IPC_NS 766 bool "IPC namespace" 767 depends on (SYSVIPC || POSIX_MQUEUE) 768 default y 769 help 770 In this namespace tasks work with IPC ids which correspond to 771 different IPC objects in different namespaces. 772 773config USER_NS 774 bool "User namespace (EXPERIMENTAL)" 775 depends on EXPERIMENTAL 776 default y 777 help 778 This allows containers, i.e. vservers, to use user namespaces 779 to provide different user info for different servers. 780 If unsure, say N. 781 782config PID_NS 783 bool "PID Namespaces" 784 default y 785 help 786 Support process id namespaces. This allows having multiple 787 processes with the same pid as long as they are in different 788 pid namespaces. This is a building block of containers. 789 790config NET_NS 791 bool "Network namespace" 792 depends on NET 793 default y 794 help 795 Allow user space to create what appear to be multiple instances 796 of the network stack. 797 798endif # NAMESPACES 799 800config SCHED_AUTOGROUP 801 bool "Automatic process group scheduling" 802 select EVENTFD 803 select CGROUPS 804 select CGROUP_SCHED 805 select FAIR_GROUP_SCHED 806 help 807 This option optimizes the scheduler for common desktop workloads by 808 automatically creating and populating task groups. This separation 809 of workloads isolates aggressive CPU burners (like build jobs) from 810 desktop applications. Task group autogeneration is currently based 811 upon task session. 812 813config MM_OWNER 814 bool 815 816config SYSFS_DEPRECATED 817 bool "enable deprecated sysfs features to support old userspace tools" 818 depends on SYSFS 819 default n 820 help 821 This option adds code that switches the layout of the "block" class 822 devices, to not show up in /sys/class/block/, but only in 823 /sys/block/. 824 825 This switch is only active when the sysfs.deprecated=1 boot option is 826 passed or the SYSFS_DEPRECATED_V2 option is set. 827 828 This option allows new kernels to run on old distributions and tools, 829 which might get confused by /sys/class/block/. Since 2007/2008 all 830 major distributions and tools handle this just fine. 831 832 Recent distributions and userspace tools after 2009/2010 depend on 833 the existence of /sys/class/block/, and will not work with this 834 option enabled. 835 836 Only if you are using a new kernel on an old distribution, you might 837 need to say Y here. 838 839config SYSFS_DEPRECATED_V2 840 bool "enabled deprecated sysfs features by default" 841 default n 842 depends on SYSFS 843 depends on SYSFS_DEPRECATED 844 help 845 Enable deprecated sysfs by default. 846 847 See the CONFIG_SYSFS_DEPRECATED option for more details about this 848 option. 849 850 Only if you are using a new kernel on an old distribution, you might 851 need to say Y here. Even then, odds are you would not need it 852 enabled, you can always pass the boot option if absolutely necessary. 853 854config RELAY 855 bool "Kernel->user space relay support (formerly relayfs)" 856 help 857 This option enables support for relay interface support in 858 certain file systems (such as debugfs). 859 It is designed to provide an efficient mechanism for tools and 860 facilities to relay large amounts of data from kernel space to 861 user space. 862 863 If unsure, say N. 864 865config BLK_DEV_INITRD 866 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 867 depends on BROKEN || !FRV 868 help 869 The initial RAM filesystem is a ramfs which is loaded by the 870 boot loader (loadlin or lilo) and that is mounted as root 871 before the normal boot procedure. It is typically used to 872 load modules needed to mount the "real" root file system, 873 etc. See <file:Documentation/initrd.txt> for details. 874 875 If RAM disk support (BLK_DEV_RAM) is also included, this 876 also enables initial RAM disk (initrd) support and adds 877 15 Kbytes (more on some other architectures) to the kernel size. 878 879 If unsure say Y. 880 881if BLK_DEV_INITRD 882 883source "usr/Kconfig" 884 885endif 886 887config CC_OPTIMIZE_FOR_SIZE 888 bool "Optimize for size" 889 default y 890 help 891 Enabling this option will pass "-Os" instead of "-O2" to gcc 892 resulting in a smaller kernel. 893 894 If unsure, say Y. 895 896config SYSCTL 897 bool 898 899config ANON_INODES 900 bool 901 902menuconfig EXPERT 903 bool "Configure standard kernel features (expert users)" 904 help 905 This option allows certain base kernel options and settings 906 to be disabled or tweaked. This is for specialized 907 environments which can tolerate a "non-standard" kernel. 908 Only use this if you really know what you are doing. 909 910config EMBEDDED 911 bool "Embedded system" 912 select EXPERT 913 help 914 This option should be enabled if compiling the kernel for 915 an embedded system so certain expert options are available 916 for configuration. 917 918config UID16 919 bool "Enable 16-bit UID system calls" if EXPERT 920 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) 921 default y 922 help 923 This enables the legacy 16-bit UID syscall wrappers. 924 925config SYSCTL_SYSCALL 926 bool "Sysctl syscall support" if EXPERT 927 depends on PROC_SYSCTL 928 default y 929 select SYSCTL 930 ---help--- 931 sys_sysctl uses binary paths that have been found challenging 932 to properly maintain and use. The interface in /proc/sys 933 using paths with ascii names is now the primary path to this 934 information. 935 936 Almost nothing using the binary sysctl interface so if you are 937 trying to save some space it is probably safe to disable this, 938 making your kernel marginally smaller. 939 940 If unsure say Y here. 941 942config KALLSYMS 943 bool "Load all symbols for debugging/ksymoops" if EXPERT 944 default y 945 help 946 Say Y here to let the kernel print out symbolic crash information and 947 symbolic stack backtraces. This increases the size of the kernel 948 somewhat, as all symbols have to be loaded into the kernel image. 949 950config KALLSYMS_ALL 951 bool "Include all symbols in kallsyms" 952 depends on DEBUG_KERNEL && KALLSYMS 953 help 954 Normally kallsyms only contains the symbols of functions, for nicer 955 OOPS messages. Some debuggers can use kallsyms for other 956 symbols too: say Y here to include all symbols, if you need them 957 and you don't care about adding 300k to the size of your kernel. 958 959 Say N. 960 961config KALLSYMS_EXTRA_PASS 962 bool "Do an extra kallsyms pass" 963 depends on KALLSYMS 964 help 965 If kallsyms is not working correctly, the build will fail with 966 inconsistent kallsyms data. If that occurs, log a bug report and 967 turn on KALLSYMS_EXTRA_PASS which should result in a stable build. 968 Always say N here unless you find a bug in kallsyms, which must be 969 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while 970 you wait for kallsyms to be fixed. 971 972 973config HOTPLUG 974 bool "Support for hot-pluggable devices" if EXPERT 975 default y 976 help 977 This option is provided for the case where no hotplug or uevent 978 capabilities is wanted by the kernel. You should only consider 979 disabling this option for embedded systems that do not use modules, a 980 dynamic /dev tree, or dynamic device discovery. Just say Y. 981 982config PRINTK 983 default y 984 bool "Enable support for printk" if EXPERT 985 help 986 This option enables normal printk support. Removing it 987 eliminates most of the message strings from the kernel image 988 and makes the kernel more or less silent. As this makes it 989 very difficult to diagnose system problems, saying N here is 990 strongly discouraged. 991 992config BUG 993 bool "BUG() support" if EXPERT 994 default y 995 help 996 Disabling this option eliminates support for BUG and WARN, reducing 997 the size of your kernel image and potentially quietly ignoring 998 numerous fatal conditions. You should only consider disabling this 999 option for embedded systems with no facilities for reporting errors. 1000 Just say Y. 1001 1002config ELF_CORE 1003 default y 1004 bool "Enable ELF core dumps" if EXPERT 1005 help 1006 Enable support for generating core dumps. Disabling saves about 4k. 1007 1008config PCSPKR_PLATFORM 1009 bool "Enable PC-Speaker support" if EXPERT 1010 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES 1011 default y 1012 help 1013 This option allows to disable the internal PC-Speaker 1014 support, saving some memory. 1015 1016config BASE_FULL 1017 default y 1018 bool "Enable full-sized data structures for core" if EXPERT 1019 help 1020 Disabling this option reduces the size of miscellaneous core 1021 kernel data structures. This saves memory on small machines, 1022 but may reduce performance. 1023 1024config FUTEX 1025 bool "Enable futex support" if EXPERT 1026 default y 1027 select RT_MUTEXES 1028 help 1029 Disabling this option will cause the kernel to be built without 1030 support for "fast userspace mutexes". The resulting kernel may not 1031 run glibc-based applications correctly. 1032 1033config EPOLL 1034 bool "Enable eventpoll support" if EXPERT 1035 default y 1036 select ANON_INODES 1037 help 1038 Disabling this option will cause the kernel to be built without 1039 support for epoll family of system calls. 1040 1041config SIGNALFD 1042 bool "Enable signalfd() system call" if EXPERT 1043 select ANON_INODES 1044 default y 1045 help 1046 Enable the signalfd() system call that allows to receive signals 1047 on a file descriptor. 1048 1049 If unsure, say Y. 1050 1051config TIMERFD 1052 bool "Enable timerfd() system call" if EXPERT 1053 select ANON_INODES 1054 default y 1055 help 1056 Enable the timerfd() system call that allows to receive timer 1057 events on a file descriptor. 1058 1059 If unsure, say Y. 1060 1061config EVENTFD 1062 bool "Enable eventfd() system call" if EXPERT 1063 select ANON_INODES 1064 default y 1065 help 1066 Enable the eventfd() system call that allows to receive both 1067 kernel notification (ie. KAIO) or userspace notifications. 1068 1069 If unsure, say Y. 1070 1071config SHMEM 1072 bool "Use full shmem filesystem" if EXPERT 1073 default y 1074 depends on MMU 1075 help 1076 The shmem is an internal filesystem used to manage shared memory. 1077 It is backed by swap and manages resource limits. It is also exported 1078 to userspace as tmpfs if TMPFS is enabled. Disabling this 1079 option replaces shmem and tmpfs with the much simpler ramfs code, 1080 which may be appropriate on small systems without swap. 1081 1082config AIO 1083 bool "Enable AIO support" if EXPERT 1084 default y 1085 help 1086 This option enables POSIX asynchronous I/O which may by used 1087 by some high performance threaded applications. Disabling 1088 this option saves about 7k. 1089 1090config HAVE_PERF_EVENTS 1091 bool 1092 help 1093 See tools/perf/design.txt for details. 1094 1095config PERF_USE_VMALLOC 1096 bool 1097 help 1098 See tools/perf/design.txt for details 1099 1100menu "Kernel Performance Events And Counters" 1101 1102config PERF_EVENTS 1103 bool "Kernel performance events and counters" 1104 default y if (PROFILING || PERF_COUNTERS) 1105 depends on HAVE_PERF_EVENTS 1106 select ANON_INODES 1107 select IRQ_WORK 1108 help 1109 Enable kernel support for various performance events provided 1110 by software and hardware. 1111 1112 Software events are supported either built-in or via the 1113 use of generic tracepoints. 1114 1115 Most modern CPUs support performance events via performance 1116 counter registers. These registers count the number of certain 1117 types of hw events: such as instructions executed, cachemisses 1118 suffered, or branches mis-predicted - without slowing down the 1119 kernel or applications. These registers can also trigger interrupts 1120 when a threshold number of events have passed - and can thus be 1121 used to profile the code that runs on that CPU. 1122 1123 The Linux Performance Event subsystem provides an abstraction of 1124 these software and hardware event capabilities, available via a 1125 system call and used by the "perf" utility in tools/perf/. It 1126 provides per task and per CPU counters, and it provides event 1127 capabilities on top of those. 1128 1129 Say Y if unsure. 1130 1131config PERF_COUNTERS 1132 bool "Kernel performance counters (old config option)" 1133 depends on HAVE_PERF_EVENTS 1134 help 1135 This config has been obsoleted by the PERF_EVENTS 1136 config option - please see that one for details. 1137 1138 It has no effect on the kernel whether you enable 1139 it or not, it is a compatibility placeholder. 1140 1141 Say N if unsure. 1142 1143config DEBUG_PERF_USE_VMALLOC 1144 default n 1145 bool "Debug: use vmalloc to back perf mmap() buffers" 1146 depends on PERF_EVENTS && DEBUG_KERNEL 1147 select PERF_USE_VMALLOC 1148 help 1149 Use vmalloc memory to back perf mmap() buffers. 1150 1151 Mostly useful for debugging the vmalloc code on platforms 1152 that don't require it. 1153 1154 Say N if unsure. 1155 1156endmenu 1157 1158config VM_EVENT_COUNTERS 1159 default y 1160 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1161 help 1162 VM event counters are needed for event counts to be shown. 1163 This option allows the disabling of the VM event counters 1164 on EXPERT systems. /proc/vmstat will only show page counts 1165 if VM event counters are disabled. 1166 1167config PCI_QUIRKS 1168 default y 1169 bool "Enable PCI quirk workarounds" if EXPERT 1170 depends on PCI 1171 help 1172 This enables workarounds for various PCI chipset 1173 bugs/quirks. Disable this only if your target machine is 1174 unaffected by PCI quirks. 1175 1176config SLUB_DEBUG 1177 default y 1178 bool "Enable SLUB debugging support" if EXPERT 1179 depends on SLUB && SYSFS 1180 help 1181 SLUB has extensive debug support features. Disabling these can 1182 result in significant savings in code size. This also disables 1183 SLUB sysfs support. /sys/slab will not exist and there will be 1184 no support for cache validation etc. 1185 1186config COMPAT_BRK 1187 bool "Disable heap randomization" 1188 default y 1189 help 1190 Randomizing heap placement makes heap exploits harder, but it 1191 also breaks ancient binaries (including anything libc5 based). 1192 This option changes the bootup default to heap randomization 1193 disabled, and can be overridden at runtime by setting 1194 /proc/sys/kernel/randomize_va_space to 2. 1195 1196 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1197 1198choice 1199 prompt "Choose SLAB allocator" 1200 default SLUB 1201 help 1202 This option allows to select a slab allocator. 1203 1204config SLAB 1205 bool "SLAB" 1206 help 1207 The regular slab allocator that is established and known to work 1208 well in all environments. It organizes cache hot objects in 1209 per cpu and per node queues. 1210 1211config SLUB 1212 bool "SLUB (Unqueued Allocator)" 1213 help 1214 SLUB is a slab allocator that minimizes cache line usage 1215 instead of managing queues of cached objects (SLAB approach). 1216 Per cpu caching is realized using slabs of objects instead 1217 of queues of objects. SLUB can use memory efficiently 1218 and has enhanced diagnostics. SLUB is the default choice for 1219 a slab allocator. 1220 1221config SLOB 1222 depends on EXPERT 1223 bool "SLOB (Simple Allocator)" 1224 help 1225 SLOB replaces the stock allocator with a drastically simpler 1226 allocator. SLOB is generally more space efficient but 1227 does not perform as well on large systems. 1228 1229endchoice 1230 1231config MMAP_ALLOW_UNINITIALIZED 1232 bool "Allow mmapped anonymous memory to be uninitialized" 1233 depends on EXPERT && !MMU 1234 default n 1235 help 1236 Normally, and according to the Linux spec, anonymous memory obtained 1237 from mmap() has it's contents cleared before it is passed to 1238 userspace. Enabling this config option allows you to request that 1239 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1240 providing a huge performance boost. If this option is not enabled, 1241 then the flag will be ignored. 1242 1243 This is taken advantage of by uClibc's malloc(), and also by 1244 ELF-FDPIC binfmt's brk and stack allocator. 1245 1246 Because of the obvious security issues, this option should only be 1247 enabled on embedded devices where you control what is run in 1248 userspace. Since that isn't generally a problem on no-MMU systems, 1249 it is normally safe to say Y here. 1250 1251 See Documentation/nommu-mmap.txt for more information. 1252 1253config PROFILING 1254 bool "Profiling support" 1255 help 1256 Say Y here to enable the extended profiling support mechanisms used 1257 by profilers such as OProfile. 1258 1259# 1260# Place an empty function call at each tracepoint site. Can be 1261# dynamically changed for a probe function. 1262# 1263config TRACEPOINTS 1264 bool 1265 1266source "arch/Kconfig" 1267 1268endmenu # General setup 1269 1270config HAVE_GENERIC_DMA_COHERENT 1271 bool 1272 default n 1273 1274config SLABINFO 1275 bool 1276 depends on PROC_FS 1277 depends on SLAB || SLUB_DEBUG 1278 default y 1279 1280config RT_MUTEXES 1281 boolean 1282 1283config BASE_SMALL 1284 int 1285 default 0 if BASE_FULL 1286 default 1 if !BASE_FULL 1287 1288menuconfig MODULES 1289 bool "Enable loadable module support" 1290 help 1291 Kernel modules are small pieces of compiled code which can 1292 be inserted in the running kernel, rather than being 1293 permanently built into the kernel. You use the "modprobe" 1294 tool to add (and sometimes remove) them. If you say Y here, 1295 many parts of the kernel can be built as modules (by 1296 answering M instead of Y where indicated): this is most 1297 useful for infrequently used options which are not required 1298 for booting. For more information, see the man pages for 1299 modprobe, lsmod, modinfo, insmod and rmmod. 1300 1301 If you say Y here, you will need to run "make 1302 modules_install" to put the modules under /lib/modules/ 1303 where modprobe can find them (you may need to be root to do 1304 this). 1305 1306 If unsure, say Y. 1307 1308if MODULES 1309 1310config MODULE_FORCE_LOAD 1311 bool "Forced module loading" 1312 default n 1313 help 1314 Allow loading of modules without version information (ie. modprobe 1315 --force). Forced module loading sets the 'F' (forced) taint flag and 1316 is usually a really bad idea. 1317 1318config MODULE_UNLOAD 1319 bool "Module unloading" 1320 help 1321 Without this option you will not be able to unload any 1322 modules (note that some modules may not be unloadable 1323 anyway), which makes your kernel smaller, faster 1324 and simpler. If unsure, say Y. 1325 1326config MODULE_FORCE_UNLOAD 1327 bool "Forced module unloading" 1328 depends on MODULE_UNLOAD && EXPERIMENTAL 1329 help 1330 This option allows you to force a module to unload, even if the 1331 kernel believes it is unsafe: the kernel will remove the module 1332 without waiting for anyone to stop using it (using the -f option to 1333 rmmod). This is mainly for kernel developers and desperate users. 1334 If unsure, say N. 1335 1336config MODVERSIONS 1337 bool "Module versioning support" 1338 help 1339 Usually, you have to use modules compiled with your kernel. 1340 Saying Y here makes it sometimes possible to use modules 1341 compiled for different kernels, by adding enough information 1342 to the modules to (hopefully) spot any changes which would 1343 make them incompatible with the kernel you are running. If 1344 unsure, say N. 1345 1346config MODULE_SRCVERSION_ALL 1347 bool "Source checksum for all modules" 1348 help 1349 Modules which contain a MODULE_VERSION get an extra "srcversion" 1350 field inserted into their modinfo section, which contains a 1351 sum of the source files which made it. This helps maintainers 1352 see exactly which source was used to build a module (since 1353 others sometimes change the module source without updating 1354 the version). With this option, such a "srcversion" field 1355 will be created for all modules. If unsure, say N. 1356 1357endif # MODULES 1358 1359config INIT_ALL_POSSIBLE 1360 bool 1361 help 1362 Back when each arch used to define their own cpu_online_map and 1363 cpu_possible_map, some of them chose to initialize cpu_possible_map 1364 with all 1s, and others with all 0s. When they were centralised, 1365 it was better to provide this option than to break all the archs 1366 and have several arch maintainers pursuing me down dark alleys. 1367 1368config STOP_MACHINE 1369 bool 1370 default y 1371 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1372 help 1373 Need stop_machine() primitive. 1374 1375source "block/Kconfig" 1376 1377config PREEMPT_NOTIFIERS 1378 bool 1379 1380config PADATA 1381 depends on SMP 1382 bool 1383 1384source "kernel/Kconfig.locks" 1385