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 These are 47 drivers that have been replaced by something else, and/or are 48 scheduled to be removed in a future kernel release. 49 50 Unless you intend to help test and develop a feature or driver that 51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 RCU_FAST_NO_HZ 400 bool "Accelerate last non-dyntick-idle CPU's grace periods" 401 depends on TREE_RCU && NO_HZ && SMP 402 default n 403 help 404 This option causes RCU to attempt to accelerate grace periods 405 in order to allow the final CPU to enter dynticks-idle state 406 more quickly. On the other hand, this option increases the 407 overhead of the dynticks-idle checking, particularly on systems 408 with large numbers of CPUs. 409 410 Say Y if energy efficiency is critically important, particularly 411 if you have relatively few CPUs. 412 413 Say N if you are unsure. 414 415config TREE_RCU_TRACE 416 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 417 select DEBUG_FS 418 help 419 This option provides tracing for the TREE_RCU and 420 TREE_PREEMPT_RCU implementations, permitting Makefile to 421 trivially select kernel/rcutree_trace.c. 422 423endmenu # "RCU Subsystem" 424 425config IKCONFIG 426 tristate "Kernel .config support" 427 ---help--- 428 This option enables the complete Linux kernel ".config" file 429 contents to be saved in the kernel. It provides documentation 430 of which kernel options are used in a running kernel or in an 431 on-disk kernel. This information can be extracted from the kernel 432 image file with the script scripts/extract-ikconfig and used as 433 input to rebuild the current kernel or to build another kernel. 434 It can also be extracted from a running kernel by reading 435 /proc/config.gz if enabled (below). 436 437config IKCONFIG_PROC 438 bool "Enable access to .config through /proc/config.gz" 439 depends on IKCONFIG && PROC_FS 440 ---help--- 441 This option enables access to the kernel configuration file 442 through /proc/config.gz. 443 444config LOG_BUF_SHIFT 445 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 446 range 12 21 447 default 17 448 help 449 Select kernel log buffer size as a power of 2. 450 Examples: 451 17 => 128 KB 452 16 => 64 KB 453 15 => 32 KB 454 14 => 16 KB 455 13 => 8 KB 456 12 => 4 KB 457 458# 459# Architectures with an unreliable sched_clock() should select this: 460# 461config HAVE_UNSTABLE_SCHED_CLOCK 462 bool 463 464menuconfig CGROUPS 465 boolean "Control Group support" 466 depends on EVENTFD 467 help 468 This option adds support for grouping sets of processes together, for 469 use with process control subsystems such as Cpusets, CFS, memory 470 controls or device isolation. 471 See 472 - Documentation/scheduler/sched-design-CFS.txt (CFS) 473 - Documentation/cgroups/ (features for grouping, isolation 474 and resource control) 475 476 Say N if unsure. 477 478if CGROUPS 479 480config CGROUP_DEBUG 481 bool "Example debug cgroup subsystem" 482 depends on CGROUPS 483 default n 484 help 485 This option enables a simple cgroup subsystem that 486 exports useful debugging information about the cgroups 487 framework. 488 489 Say N if unsure. 490 491config CGROUP_NS 492 bool "Namespace cgroup subsystem" 493 depends on CGROUPS 494 help 495 Provides a simple namespace cgroup subsystem to 496 provide hierarchical naming of sets of namespaces, 497 for instance virtual servers and checkpoint/restart 498 jobs. 499 500config CGROUP_FREEZER 501 bool "Freezer cgroup subsystem" 502 depends on CGROUPS 503 help 504 Provides a way to freeze and unfreeze all tasks in a 505 cgroup. 506 507config CGROUP_DEVICE 508 bool "Device controller for cgroups" 509 depends on CGROUPS && EXPERIMENTAL 510 help 511 Provides a cgroup implementing whitelists for devices which 512 a process in the cgroup can mknod or open. 513 514config CPUSETS 515 bool "Cpuset support" 516 depends on CGROUPS 517 help 518 This option will let you create and manage CPUSETs which 519 allow dynamically partitioning a system into sets of CPUs and 520 Memory Nodes and assigning tasks to run only within those sets. 521 This is primarily useful on large SMP or NUMA systems. 522 523 Say N if unsure. 524 525config PROC_PID_CPUSET 526 bool "Include legacy /proc/<pid>/cpuset file" 527 depends on CPUSETS 528 default y 529 530config CGROUP_CPUACCT 531 bool "Simple CPU accounting cgroup subsystem" 532 depends on CGROUPS 533 help 534 Provides a simple Resource Controller for monitoring the 535 total CPU consumed by the tasks in a cgroup. 536 537config RESOURCE_COUNTERS 538 bool "Resource counters" 539 help 540 This option enables controller independent resource accounting 541 infrastructure that works with cgroups. 542 depends on CGROUPS 543 544config CGROUP_MEM_RES_CTLR 545 bool "Memory Resource Controller for Control Groups" 546 depends on CGROUPS && RESOURCE_COUNTERS 547 select MM_OWNER 548 help 549 Provides a memory resource controller that manages both anonymous 550 memory and page cache. (See Documentation/cgroups/memory.txt) 551 552 Note that setting this option increases fixed memory overhead 553 associated with each page of memory in the system. By this, 554 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 555 usage tracking struct at boot. Total amount of this is printed out 556 at boot. 557 558 Only enable when you're ok with these trade offs and really 559 sure you need the memory resource controller. Even when you enable 560 this, you can set "cgroup_disable=memory" at your boot option to 561 disable memory resource controller and you can avoid overheads. 562 (and lose benefits of memory resource controller) 563 564 This config option also selects MM_OWNER config option, which 565 could in turn add some fork/exit overhead. 566 567config CGROUP_MEM_RES_CTLR_SWAP 568 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)" 569 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL 570 help 571 Add swap management feature to memory resource controller. When you 572 enable this, you can limit mem+swap usage per cgroup. In other words, 573 when you disable this, memory resource controller has no cares to 574 usage of swap...a process can exhaust all of the swap. This extension 575 is useful when you want to avoid exhaustion swap but this itself 576 adds more overheads and consumes memory for remembering information. 577 Especially if you use 32bit system or small memory system, please 578 be careful about enabling this. When memory resource controller 579 is disabled by boot option, this will be automatically disabled and 580 there will be no overhead from this. Even when you set this config=y, 581 if boot option "noswapaccount" is set, swap will not be accounted. 582 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 583 size is 4096bytes, 512k per 1Gbytes of swap. 584 585menuconfig CGROUP_SCHED 586 bool "Group CPU scheduler" 587 depends on EXPERIMENTAL && CGROUPS 588 default n 589 help 590 This feature lets CPU scheduler recognize task groups and control CPU 591 bandwidth allocation to such task groups. It uses cgroups to group 592 tasks. 593 594if CGROUP_SCHED 595config FAIR_GROUP_SCHED 596 bool "Group scheduling for SCHED_OTHER" 597 depends on CGROUP_SCHED 598 default CGROUP_SCHED 599 600config RT_GROUP_SCHED 601 bool "Group scheduling for SCHED_RR/FIFO" 602 depends on EXPERIMENTAL 603 depends on CGROUP_SCHED 604 default n 605 help 606 This feature lets you explicitly allocate real CPU bandwidth 607 to task groups. If enabled, it will also make it impossible to 608 schedule realtime tasks for non-root users until you allocate 609 realtime bandwidth for them. 610 See Documentation/scheduler/sched-rt-group.txt for more information. 611 612endif #CGROUP_SCHED 613 614config BLK_CGROUP 615 tristate "Block IO controller" 616 depends on CGROUPS && BLOCK 617 default n 618 ---help--- 619 Generic block IO controller cgroup interface. This is the common 620 cgroup interface which should be used by various IO controlling 621 policies. 622 623 Currently, CFQ IO scheduler uses it to recognize task groups and 624 control disk bandwidth allocation (proportional time slice allocation) 625 to such task groups. 626 627 This option only enables generic Block IO controller infrastructure. 628 One needs to also enable actual IO controlling logic in CFQ for it 629 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y). 630 631 See Documentation/cgroups/blkio-controller.txt for more information. 632 633config DEBUG_BLK_CGROUP 634 bool "Enable Block IO controller debugging" 635 depends on BLK_CGROUP 636 default n 637 ---help--- 638 Enable some debugging help. Currently it exports additional stat 639 files in a cgroup which can be useful for debugging. 640 641endif # CGROUPS 642 643config MM_OWNER 644 bool 645 646config SYSFS_DEPRECATED 647 bool 648 649config SYSFS_DEPRECATED_V2 650 bool "enable deprecated sysfs features to support old userspace tools" 651 depends on SYSFS 652 default n 653 select SYSFS_DEPRECATED 654 help 655 This option switches the layout of sysfs to the deprecated 656 version. Do not use it on recent distributions. 657 658 The current sysfs layout features a unified device tree at 659 /sys/devices/, which is able to express a hierarchy between 660 class devices. If the deprecated option is set to Y, the 661 unified device tree is split into a bus device tree at 662 /sys/devices/ and several individual class device trees at 663 /sys/class/. The class and bus devices will be connected by 664 "<subsystem>:<name>" and the "device" links. The "block" 665 class devices, will not show up in /sys/class/block/. Some 666 subsystems will suppress the creation of some devices which 667 depend on the unified device tree. 668 669 This option is not a pure compatibility option that can 670 be safely enabled on newer distributions. It will change the 671 layout of sysfs to the non-extensible deprecated version, 672 and disable some features, which can not be exported without 673 confusing older userspace tools. Since 2007/2008 all major 674 distributions do not enable this option, and ship no tools which 675 depend on the deprecated layout or this option. 676 677 If you are using a new kernel on an older distribution, or use 678 older userspace tools, you might need to say Y here. Do not say Y, 679 if the original kernel, that came with your distribution, has 680 this option set to N. 681 682config RELAY 683 bool "Kernel->user space relay support (formerly relayfs)" 684 help 685 This option enables support for relay interface support in 686 certain file systems (such as debugfs). 687 It is designed to provide an efficient mechanism for tools and 688 facilities to relay large amounts of data from kernel space to 689 user space. 690 691 If unsure, say N. 692 693config NAMESPACES 694 bool "Namespaces support" if EMBEDDED 695 default !EMBEDDED 696 help 697 Provides the way to make tasks work with different objects using 698 the same id. For example same IPC id may refer to different objects 699 or same user id or pid may refer to different tasks when used in 700 different namespaces. 701 702config UTS_NS 703 bool "UTS namespace" 704 depends on NAMESPACES 705 help 706 In this namespace tasks see different info provided with the 707 uname() system call 708 709config IPC_NS 710 bool "IPC namespace" 711 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE) 712 help 713 In this namespace tasks work with IPC ids which correspond to 714 different IPC objects in different namespaces. 715 716config USER_NS 717 bool "User namespace (EXPERIMENTAL)" 718 depends on NAMESPACES && EXPERIMENTAL 719 help 720 This allows containers, i.e. vservers, to use user namespaces 721 to provide different user info for different servers. 722 If unsure, say N. 723 724config PID_NS 725 bool "PID Namespaces (EXPERIMENTAL)" 726 default n 727 depends on NAMESPACES && EXPERIMENTAL 728 help 729 Support process id namespaces. This allows having multiple 730 processes with the same pid as long as they are in different 731 pid namespaces. This is a building block of containers. 732 733 Unless you want to work with an experimental feature 734 say N here. 735 736config NET_NS 737 bool "Network namespace" 738 default n 739 depends on NAMESPACES && EXPERIMENTAL && NET 740 help 741 Allow user space to create what appear to be multiple instances 742 of the network stack. 743 744config BLK_DEV_INITRD 745 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 746 depends on BROKEN || !FRV 747 help 748 The initial RAM filesystem is a ramfs which is loaded by the 749 boot loader (loadlin or lilo) and that is mounted as root 750 before the normal boot procedure. It is typically used to 751 load modules needed to mount the "real" root file system, 752 etc. See <file:Documentation/initrd.txt> for details. 753 754 If RAM disk support (BLK_DEV_RAM) is also included, this 755 also enables initial RAM disk (initrd) support and adds 756 15 Kbytes (more on some other architectures) to the kernel size. 757 758 If unsure say Y. 759 760if BLK_DEV_INITRD 761 762source "usr/Kconfig" 763 764endif 765 766config CC_OPTIMIZE_FOR_SIZE 767 bool "Optimize for size" 768 default y 769 help 770 Enabling this option will pass "-Os" instead of "-O2" to gcc 771 resulting in a smaller kernel. 772 773 If unsure, say Y. 774 775config SYSCTL 776 bool 777 778config ANON_INODES 779 bool 780 781menuconfig EMBEDDED 782 bool "Configure standard kernel features (for small systems)" 783 help 784 This option allows certain base kernel options and settings 785 to be disabled or tweaked. This is for specialized 786 environments which can tolerate a "non-standard" kernel. 787 Only use this if you really know what you are doing. 788 789config UID16 790 bool "Enable 16-bit UID system calls" if EMBEDDED 791 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) 792 default y 793 help 794 This enables the legacy 16-bit UID syscall wrappers. 795 796config SYSCTL_SYSCALL 797 bool "Sysctl syscall support" if EMBEDDED 798 depends on PROC_SYSCTL 799 default y 800 select SYSCTL 801 ---help--- 802 sys_sysctl uses binary paths that have been found challenging 803 to properly maintain and use. The interface in /proc/sys 804 using paths with ascii names is now the primary path to this 805 information. 806 807 Almost nothing using the binary sysctl interface so if you are 808 trying to save some space it is probably safe to disable this, 809 making your kernel marginally smaller. 810 811 If unsure say Y here. 812 813config KALLSYMS 814 bool "Load all symbols for debugging/ksymoops" if EMBEDDED 815 default y 816 help 817 Say Y here to let the kernel print out symbolic crash information and 818 symbolic stack backtraces. This increases the size of the kernel 819 somewhat, as all symbols have to be loaded into the kernel image. 820 821config KALLSYMS_ALL 822 bool "Include all symbols in kallsyms" 823 depends on DEBUG_KERNEL && KALLSYMS 824 help 825 Normally kallsyms only contains the symbols of functions, for nicer 826 OOPS messages. Some debuggers can use kallsyms for other 827 symbols too: say Y here to include all symbols, if you need them 828 and you don't care about adding 300k to the size of your kernel. 829 830 Say N. 831 832config KALLSYMS_EXTRA_PASS 833 bool "Do an extra kallsyms pass" 834 depends on KALLSYMS 835 help 836 If kallsyms is not working correctly, the build will fail with 837 inconsistent kallsyms data. If that occurs, log a bug report and 838 turn on KALLSYMS_EXTRA_PASS which should result in a stable build. 839 Always say N here unless you find a bug in kallsyms, which must be 840 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while 841 you wait for kallsyms to be fixed. 842 843 844config HOTPLUG 845 bool "Support for hot-pluggable devices" if EMBEDDED 846 default y 847 help 848 This option is provided for the case where no hotplug or uevent 849 capabilities is wanted by the kernel. You should only consider 850 disabling this option for embedded systems that do not use modules, a 851 dynamic /dev tree, or dynamic device discovery. Just say Y. 852 853config PRINTK 854 default y 855 bool "Enable support for printk" if EMBEDDED 856 help 857 This option enables normal printk support. Removing it 858 eliminates most of the message strings from the kernel image 859 and makes the kernel more or less silent. As this makes it 860 very difficult to diagnose system problems, saying N here is 861 strongly discouraged. 862 863config BUG 864 bool "BUG() support" if EMBEDDED 865 default y 866 help 867 Disabling this option eliminates support for BUG and WARN, reducing 868 the size of your kernel image and potentially quietly ignoring 869 numerous fatal conditions. You should only consider disabling this 870 option for embedded systems with no facilities for reporting errors. 871 Just say Y. 872 873config ELF_CORE 874 default y 875 bool "Enable ELF core dumps" if EMBEDDED 876 help 877 Enable support for generating core dumps. Disabling saves about 4k. 878 879config PCSPKR_PLATFORM 880 bool "Enable PC-Speaker support" if EMBEDDED 881 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES 882 default y 883 help 884 This option allows to disable the internal PC-Speaker 885 support, saving some memory. 886 887config BASE_FULL 888 default y 889 bool "Enable full-sized data structures for core" if EMBEDDED 890 help 891 Disabling this option reduces the size of miscellaneous core 892 kernel data structures. This saves memory on small machines, 893 but may reduce performance. 894 895config FUTEX 896 bool "Enable futex support" if EMBEDDED 897 default y 898 select RT_MUTEXES 899 help 900 Disabling this option will cause the kernel to be built without 901 support for "fast userspace mutexes". The resulting kernel may not 902 run glibc-based applications correctly. 903 904config EPOLL 905 bool "Enable eventpoll support" if EMBEDDED 906 default y 907 select ANON_INODES 908 help 909 Disabling this option will cause the kernel to be built without 910 support for epoll family of system calls. 911 912config SIGNALFD 913 bool "Enable signalfd() system call" if EMBEDDED 914 select ANON_INODES 915 default y 916 help 917 Enable the signalfd() system call that allows to receive signals 918 on a file descriptor. 919 920 If unsure, say Y. 921 922config TIMERFD 923 bool "Enable timerfd() system call" if EMBEDDED 924 select ANON_INODES 925 default y 926 help 927 Enable the timerfd() system call that allows to receive timer 928 events on a file descriptor. 929 930 If unsure, say Y. 931 932config EVENTFD 933 bool "Enable eventfd() system call" if EMBEDDED 934 select ANON_INODES 935 default y 936 help 937 Enable the eventfd() system call that allows to receive both 938 kernel notification (ie. KAIO) or userspace notifications. 939 940 If unsure, say Y. 941 942config SHMEM 943 bool "Use full shmem filesystem" if EMBEDDED 944 default y 945 depends on MMU 946 help 947 The shmem is an internal filesystem used to manage shared memory. 948 It is backed by swap and manages resource limits. It is also exported 949 to userspace as tmpfs if TMPFS is enabled. Disabling this 950 option replaces shmem and tmpfs with the much simpler ramfs code, 951 which may be appropriate on small systems without swap. 952 953config AIO 954 bool "Enable AIO support" if EMBEDDED 955 default y 956 help 957 This option enables POSIX asynchronous I/O which may by used 958 by some high performance threaded applications. Disabling 959 this option saves about 7k. 960 961config HAVE_PERF_EVENTS 962 bool 963 help 964 See tools/perf/design.txt for details. 965 966config PERF_USE_VMALLOC 967 bool 968 help 969 See tools/perf/design.txt for details 970 971menu "Kernel Performance Events And Counters" 972 973config PERF_EVENTS 974 bool "Kernel performance events and counters" 975 default y if (PROFILING || PERF_COUNTERS) 976 depends on HAVE_PERF_EVENTS 977 select ANON_INODES 978 help 979 Enable kernel support for various performance events provided 980 by software and hardware. 981 982 Software events are supported either built-in or via the 983 use of generic tracepoints. 984 985 Most modern CPUs support performance events via performance 986 counter registers. These registers count the number of certain 987 types of hw events: such as instructions executed, cachemisses 988 suffered, or branches mis-predicted - without slowing down the 989 kernel or applications. These registers can also trigger interrupts 990 when a threshold number of events have passed - and can thus be 991 used to profile the code that runs on that CPU. 992 993 The Linux Performance Event subsystem provides an abstraction of 994 these software and hardware event capabilities, available via a 995 system call and used by the "perf" utility in tools/perf/. It 996 provides per task and per CPU counters, and it provides event 997 capabilities on top of those. 998 999 Say Y if unsure. 1000 1001config PERF_COUNTERS 1002 bool "Kernel performance counters (old config option)" 1003 depends on HAVE_PERF_EVENTS 1004 help 1005 This config has been obsoleted by the PERF_EVENTS 1006 config option - please see that one for details. 1007 1008 It has no effect on the kernel whether you enable 1009 it or not, it is a compatibility placeholder. 1010 1011 Say N if unsure. 1012 1013config DEBUG_PERF_USE_VMALLOC 1014 default n 1015 bool "Debug: use vmalloc to back perf mmap() buffers" 1016 depends on PERF_EVENTS && DEBUG_KERNEL 1017 select PERF_USE_VMALLOC 1018 help 1019 Use vmalloc memory to back perf mmap() buffers. 1020 1021 Mostly useful for debugging the vmalloc code on platforms 1022 that don't require it. 1023 1024 Say N if unsure. 1025 1026endmenu 1027 1028config VM_EVENT_COUNTERS 1029 default y 1030 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED 1031 help 1032 VM event counters are needed for event counts to be shown. 1033 This option allows the disabling of the VM event counters 1034 on EMBEDDED systems. /proc/vmstat will only show page counts 1035 if VM event counters are disabled. 1036 1037config PCI_QUIRKS 1038 default y 1039 bool "Enable PCI quirk workarounds" if EMBEDDED 1040 depends on PCI 1041 help 1042 This enables workarounds for various PCI chipset 1043 bugs/quirks. Disable this only if your target machine is 1044 unaffected by PCI quirks. 1045 1046config SLUB_DEBUG 1047 default y 1048 bool "Enable SLUB debugging support" if EMBEDDED 1049 depends on SLUB && SYSFS 1050 help 1051 SLUB has extensive debug support features. Disabling these can 1052 result in significant savings in code size. This also disables 1053 SLUB sysfs support. /sys/slab will not exist and there will be 1054 no support for cache validation etc. 1055 1056config COMPAT_BRK 1057 bool "Disable heap randomization" 1058 default y 1059 help 1060 Randomizing heap placement makes heap exploits harder, but it 1061 also breaks ancient binaries (including anything libc5 based). 1062 This option changes the bootup default to heap randomization 1063 disabled, and can be overridden at runtime by setting 1064 /proc/sys/kernel/randomize_va_space to 2. 1065 1066 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1067 1068choice 1069 prompt "Choose SLAB allocator" 1070 default SLUB 1071 help 1072 This option allows to select a slab allocator. 1073 1074config SLAB 1075 bool "SLAB" 1076 help 1077 The regular slab allocator that is established and known to work 1078 well in all environments. It organizes cache hot objects in 1079 per cpu and per node queues. 1080 1081config SLUB 1082 bool "SLUB (Unqueued Allocator)" 1083 help 1084 SLUB is a slab allocator that minimizes cache line usage 1085 instead of managing queues of cached objects (SLAB approach). 1086 Per cpu caching is realized using slabs of objects instead 1087 of queues of objects. SLUB can use memory efficiently 1088 and has enhanced diagnostics. SLUB is the default choice for 1089 a slab allocator. 1090 1091config SLOB 1092 depends on EMBEDDED 1093 bool "SLOB (Simple Allocator)" 1094 help 1095 SLOB replaces the stock allocator with a drastically simpler 1096 allocator. SLOB is generally more space efficient but 1097 does not perform as well on large systems. 1098 1099endchoice 1100 1101config MMAP_ALLOW_UNINITIALIZED 1102 bool "Allow mmapped anonymous memory to be uninitialized" 1103 depends on EMBEDDED && !MMU 1104 default n 1105 help 1106 Normally, and according to the Linux spec, anonymous memory obtained 1107 from mmap() has it's contents cleared before it is passed to 1108 userspace. Enabling this config option allows you to request that 1109 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1110 providing a huge performance boost. If this option is not enabled, 1111 then the flag will be ignored. 1112 1113 This is taken advantage of by uClibc's malloc(), and also by 1114 ELF-FDPIC binfmt's brk and stack allocator. 1115 1116 Because of the obvious security issues, this option should only be 1117 enabled on embedded devices where you control what is run in 1118 userspace. Since that isn't generally a problem on no-MMU systems, 1119 it is normally safe to say Y here. 1120 1121 See Documentation/nommu-mmap.txt for more information. 1122 1123config PROFILING 1124 bool "Profiling support" 1125 help 1126 Say Y here to enable the extended profiling support mechanisms used 1127 by profilers such as OProfile. 1128 1129# 1130# Place an empty function call at each tracepoint site. Can be 1131# dynamically changed for a probe function. 1132# 1133config TRACEPOINTS 1134 bool 1135 1136source "arch/Kconfig" 1137 1138config SLOW_WORK 1139 default n 1140 bool 1141 help 1142 The slow work thread pool provides a number of dynamically allocated 1143 threads that can be used by the kernel to perform operations that 1144 take a relatively long time. 1145 1146 An example of this would be CacheFiles doing a path lookup followed 1147 by a series of mkdirs and a create call, all of which have to touch 1148 disk. 1149 1150 See Documentation/slow-work.txt. 1151 1152config SLOW_WORK_DEBUG 1153 bool "Slow work debugging through debugfs" 1154 default n 1155 depends on SLOW_WORK && DEBUG_FS 1156 help 1157 Display the contents of the slow work run queue through debugfs, 1158 including items currently executing. 1159 1160 See Documentation/slow-work.txt. 1161 1162endmenu # General setup 1163 1164config HAVE_GENERIC_DMA_COHERENT 1165 bool 1166 default n 1167 1168config SLABINFO 1169 bool 1170 depends on PROC_FS 1171 depends on SLAB || SLUB_DEBUG 1172 default y 1173 1174config RT_MUTEXES 1175 boolean 1176 1177config BASE_SMALL 1178 int 1179 default 0 if BASE_FULL 1180 default 1 if !BASE_FULL 1181 1182menuconfig MODULES 1183 bool "Enable loadable module support" 1184 help 1185 Kernel modules are small pieces of compiled code which can 1186 be inserted in the running kernel, rather than being 1187 permanently built into the kernel. You use the "modprobe" 1188 tool to add (and sometimes remove) them. If you say Y here, 1189 many parts of the kernel can be built as modules (by 1190 answering M instead of Y where indicated): this is most 1191 useful for infrequently used options which are not required 1192 for booting. For more information, see the man pages for 1193 modprobe, lsmod, modinfo, insmod and rmmod. 1194 1195 If you say Y here, you will need to run "make 1196 modules_install" to put the modules under /lib/modules/ 1197 where modprobe can find them (you may need to be root to do 1198 this). 1199 1200 If unsure, say Y. 1201 1202if MODULES 1203 1204config MODULE_FORCE_LOAD 1205 bool "Forced module loading" 1206 default n 1207 help 1208 Allow loading of modules without version information (ie. modprobe 1209 --force). Forced module loading sets the 'F' (forced) taint flag and 1210 is usually a really bad idea. 1211 1212config MODULE_UNLOAD 1213 bool "Module unloading" 1214 help 1215 Without this option you will not be able to unload any 1216 modules (note that some modules may not be unloadable 1217 anyway), which makes your kernel smaller, faster 1218 and simpler. If unsure, say Y. 1219 1220config MODULE_FORCE_UNLOAD 1221 bool "Forced module unloading" 1222 depends on MODULE_UNLOAD && EXPERIMENTAL 1223 help 1224 This option allows you to force a module to unload, even if the 1225 kernel believes it is unsafe: the kernel will remove the module 1226 without waiting for anyone to stop using it (using the -f option to 1227 rmmod). This is mainly for kernel developers and desperate users. 1228 If unsure, say N. 1229 1230config MODVERSIONS 1231 bool "Module versioning support" 1232 help 1233 Usually, you have to use modules compiled with your kernel. 1234 Saying Y here makes it sometimes possible to use modules 1235 compiled for different kernels, by adding enough information 1236 to the modules to (hopefully) spot any changes which would 1237 make them incompatible with the kernel you are running. If 1238 unsure, say N. 1239 1240config MODULE_SRCVERSION_ALL 1241 bool "Source checksum for all modules" 1242 help 1243 Modules which contain a MODULE_VERSION get an extra "srcversion" 1244 field inserted into their modinfo section, which contains a 1245 sum of the source files which made it. This helps maintainers 1246 see exactly which source was used to build a module (since 1247 others sometimes change the module source without updating 1248 the version). With this option, such a "srcversion" field 1249 will be created for all modules. If unsure, say N. 1250 1251endif # MODULES 1252 1253config INIT_ALL_POSSIBLE 1254 bool 1255 help 1256 Back when each arch used to define their own cpu_online_map and 1257 cpu_possible_map, some of them chose to initialize cpu_possible_map 1258 with all 1s, and others with all 0s. When they were centralised, 1259 it was better to provide this option than to break all the archs 1260 and have several arch maintainers pursuing me down dark alleys. 1261 1262config STOP_MACHINE 1263 bool 1264 default y 1265 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1266 help 1267 Need stop_machine() primitive. 1268 1269source "block/Kconfig" 1270 1271config PREEMPT_NOTIFIERS 1272 bool 1273 1274config PADATA 1275 depends on SMP 1276 bool 1277 1278source "kernel/Kconfig.locks" 1279