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 19menu "General setup" 20 21config EXPERIMENTAL 22 bool "Prompt for development and/or incomplete code/drivers" 23 ---help--- 24 Some of the various things that Linux supports (such as network 25 drivers, file systems, network protocols, etc.) can be in a state 26 of development where the functionality, stability, or the level of 27 testing is not yet high enough for general use. This is usually 28 known as the "alpha-test" phase among developers. If a feature is 29 currently in alpha-test, then the developers usually discourage 30 uninformed widespread use of this feature by the general public to 31 avoid "Why doesn't this work?" type mail messages. However, active 32 testing and use of these systems is welcomed. Just be aware that it 33 may not meet the normal level of reliability or it may fail to work 34 in some special cases. Detailed bug reports from people familiar 35 with the kernel internals are usually welcomed by the developers 36 (before submitting bug reports, please read the documents 37 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 38 <file:Documentation/BUG-HUNTING>, and 39 <file:Documentation/oops-tracing.txt> in the kernel source). 40 41 This option will also make obsoleted drivers available. These are 42 drivers that have been replaced by something else, and/or are 43 scheduled to be removed in a future kernel release. 44 45 Unless you intend to help test and develop a feature or driver that 46 falls into this category, or you have a situation that requires 47 using these features, you should probably say N here, which will 48 cause the configurator to present you with fewer choices. If 49 you say Y here, you will be offered the choice of using features or 50 drivers that are currently considered to be in the alpha-test phase. 51 52config BROKEN 53 bool 54 55config BROKEN_ON_SMP 56 bool 57 depends on BROKEN || !SMP 58 default y 59 60config LOCK_KERNEL 61 bool 62 depends on SMP || PREEMPT 63 default y 64 65config INIT_ENV_ARG_LIMIT 66 int 67 default 32 if !UML 68 default 128 if UML 69 help 70 Maximum of each of the number of arguments and environment 71 variables passed to init from the kernel command line. 72 73 74config LOCALVERSION 75 string "Local version - append to kernel release" 76 help 77 Append an extra string to the end of your kernel version. 78 This will show up when you type uname, for example. 79 The string you set here will be appended after the contents of 80 any files with a filename matching localversion* in your 81 object and source tree, in that order. Your total string can 82 be a maximum of 64 characters. 83 84config LOCALVERSION_AUTO 85 bool "Automatically append version information to the version string" 86 default y 87 help 88 This will try to automatically determine if the current tree is a 89 release tree by looking for git tags that belong to the current 90 top of tree revision. 91 92 A string of the format -gxxxxxxxx will be added to the localversion 93 if a git-based tree is found. The string generated by this will be 94 appended after any matching localversion* files, and after the value 95 set in CONFIG_LOCALVERSION. 96 97 (The actual string used here is the first eight characters produced 98 by running the command: 99 100 $ git rev-parse --verify HEAD 101 102 which is done within the script "scripts/setlocalversion".) 103 104config HAVE_KERNEL_GZIP 105 bool 106 107config HAVE_KERNEL_BZIP2 108 bool 109 110config HAVE_KERNEL_LZMA 111 bool 112 113choice 114 prompt "Kernel compression mode" 115 default KERNEL_GZIP 116 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA 117 help 118 The linux kernel is a kind of self-extracting executable. 119 Several compression algorithms are available, which differ 120 in efficiency, compression and decompression speed. 121 Compression speed is only relevant when building a kernel. 122 Decompression speed is relevant at each boot. 123 124 If you have any problems with bzip2 or lzma compressed 125 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 126 version of this functionality (bzip2 only), for 2.4, was 127 supplied by Christian Ludwig) 128 129 High compression options are mostly useful for users, who 130 are low on disk space (embedded systems), but for whom ram 131 size matters less. 132 133 If in doubt, select 'gzip' 134 135config KERNEL_GZIP 136 bool "Gzip" 137 depends on HAVE_KERNEL_GZIP 138 help 139 The old and tried gzip compression. Its compression ratio is 140 the poorest among the 3 choices; however its speed (both 141 compression and decompression) is the fastest. 142 143config KERNEL_BZIP2 144 bool "Bzip2" 145 depends on HAVE_KERNEL_BZIP2 146 help 147 Its compression ratio and speed is intermediate. 148 Decompression speed is slowest among the three. The kernel 149 size is about 10% smaller with bzip2, in comparison to gzip. 150 Bzip2 uses a large amount of memory. For modern kernels you 151 will need at least 8MB RAM or more for booting. 152 153config KERNEL_LZMA 154 bool "LZMA" 155 depends on HAVE_KERNEL_LZMA 156 help 157 The most recent compression algorithm. 158 Its ratio is best, decompression speed is between the other 159 two. Compression is slowest. The kernel size is about 33% 160 smaller with LZMA in comparison to gzip. 161 162endchoice 163 164config SWAP 165 bool "Support for paging of anonymous memory (swap)" 166 depends on MMU && BLOCK 167 default y 168 help 169 This option allows you to choose whether you want to have support 170 for so called swap devices or swap files in your kernel that are 171 used to provide more virtual memory than the actual RAM present 172 in your computer. If unsure say Y. 173 174config SYSVIPC 175 bool "System V IPC" 176 ---help--- 177 Inter Process Communication is a suite of library functions and 178 system calls which let processes (running programs) synchronize and 179 exchange information. It is generally considered to be a good thing, 180 and some programs won't run unless you say Y here. In particular, if 181 you want to run the DOS emulator dosemu under Linux (read the 182 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 183 you'll need to say Y here. 184 185 You can find documentation about IPC with "info ipc" and also in 186 section 6.4 of the Linux Programmer's Guide, available from 187 <http://www.tldp.org/guides.html>. 188 189config SYSVIPC_SYSCTL 190 bool 191 depends on SYSVIPC 192 depends on SYSCTL 193 default y 194 195config POSIX_MQUEUE 196 bool "POSIX Message Queues" 197 depends on NET && EXPERIMENTAL 198 ---help--- 199 POSIX variant of message queues is a part of IPC. In POSIX message 200 queues every message has a priority which decides about succession 201 of receiving it by a process. If you want to compile and run 202 programs written e.g. for Solaris with use of its POSIX message 203 queues (functions mq_*) say Y here. 204 205 POSIX message queues are visible as a filesystem called 'mqueue' 206 and can be mounted somewhere if you want to do filesystem 207 operations on message queues. 208 209 If unsure, say Y. 210 211config POSIX_MQUEUE_SYSCTL 212 bool 213 depends on POSIX_MQUEUE 214 depends on SYSCTL 215 default y 216 217config BSD_PROCESS_ACCT 218 bool "BSD Process Accounting" 219 help 220 If you say Y here, a user level program will be able to instruct the 221 kernel (via a special system call) to write process accounting 222 information to a file: whenever a process exits, information about 223 that process will be appended to the file by the kernel. The 224 information includes things such as creation time, owning user, 225 command name, memory usage, controlling terminal etc. (the complete 226 list is in the struct acct in <file:include/linux/acct.h>). It is 227 up to the user level program to do useful things with this 228 information. This is generally a good idea, so say Y. 229 230config BSD_PROCESS_ACCT_V3 231 bool "BSD Process Accounting version 3 file format" 232 depends on BSD_PROCESS_ACCT 233 default n 234 help 235 If you say Y here, the process accounting information is written 236 in a new file format that also logs the process IDs of each 237 process and it's parent. Note that this file format is incompatible 238 with previous v0/v1/v2 file formats, so you will need updated tools 239 for processing it. A preliminary version of these tools is available 240 at <http://www.gnu.org/software/acct/>. 241 242config TASKSTATS 243 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 244 depends on NET 245 default n 246 help 247 Export selected statistics for tasks/processes through the 248 generic netlink interface. Unlike BSD process accounting, the 249 statistics are available during the lifetime of tasks/processes as 250 responses to commands. Like BSD accounting, they are sent to user 251 space on task exit. 252 253 Say N if unsure. 254 255config TASK_DELAY_ACCT 256 bool "Enable per-task delay accounting (EXPERIMENTAL)" 257 depends on TASKSTATS 258 help 259 Collect information on time spent by a task waiting for system 260 resources like cpu, synchronous block I/O completion and swapping 261 in pages. Such statistics can help in setting a task's priorities 262 relative to other tasks for cpu, io, rss limits etc. 263 264 Say N if unsure. 265 266config TASK_XACCT 267 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 268 depends on TASKSTATS 269 help 270 Collect extended task accounting data and send the data 271 to userland for processing over the taskstats interface. 272 273 Say N if unsure. 274 275config TASK_IO_ACCOUNTING 276 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 277 depends on TASK_XACCT 278 help 279 Collect information on the number of bytes of storage I/O which this 280 task has caused. 281 282 Say N if unsure. 283 284config AUDIT 285 bool "Auditing support" 286 depends on NET 287 help 288 Enable auditing infrastructure that can be used with another 289 kernel subsystem, such as SELinux (which requires this for 290 logging of avc messages output). Does not do system-call 291 auditing without CONFIG_AUDITSYSCALL. 292 293config AUDITSYSCALL 294 bool "Enable system-call auditing support" 295 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH) 296 default y if SECURITY_SELINUX 297 help 298 Enable low-overhead system-call auditing infrastructure that 299 can be used independently or with another kernel subsystem, 300 such as SELinux. To use audit's filesystem watch feature, please 301 ensure that INOTIFY is configured. 302 303config AUDIT_TREE 304 def_bool y 305 depends on AUDITSYSCALL 306 select INOTIFY 307 308menu "RCU Subsystem" 309 310choice 311 prompt "RCU Implementation" 312 default TREE_RCU 313 314config CLASSIC_RCU 315 bool "Classic RCU" 316 help 317 This option selects the classic RCU implementation that is 318 designed for best read-side performance on non-realtime 319 systems. 320 321 Select this option if you are unsure. 322 323config TREE_RCU 324 bool "Tree-based hierarchical RCU" 325 help 326 This option selects the RCU implementation that is 327 designed for very large SMP system with hundreds or 328 thousands of CPUs. 329 330config PREEMPT_RCU 331 bool "Preemptible RCU" 332 depends on PREEMPT 333 help 334 This option reduces the latency of the kernel by making certain 335 RCU sections preemptible. Normally RCU code is non-preemptible, if 336 this option is selected then read-only RCU sections become 337 preemptible. This helps latency, but may expose bugs due to 338 now-naive assumptions about each RCU read-side critical section 339 remaining on a given CPU through its execution. 340 341endchoice 342 343config RCU_TRACE 344 bool "Enable tracing for RCU" 345 depends on TREE_RCU || PREEMPT_RCU 346 help 347 This option provides tracing in RCU which presents stats 348 in debugfs for debugging RCU implementation. 349 350 Say Y here if you want to enable RCU tracing 351 Say N if you are unsure. 352 353config RCU_FANOUT 354 int "Tree-based hierarchical RCU fanout value" 355 range 2 64 if 64BIT 356 range 2 32 if !64BIT 357 depends on TREE_RCU 358 default 64 if 64BIT 359 default 32 if !64BIT 360 help 361 This option controls the fanout of hierarchical implementations 362 of RCU, allowing RCU to work efficiently on machines with 363 large numbers of CPUs. This value must be at least the cube 364 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit 365 systems and up to 262,144 for 64-bit systems. 366 367 Select a specific number if testing RCU itself. 368 Take the default if unsure. 369 370config RCU_FANOUT_EXACT 371 bool "Disable tree-based hierarchical RCU auto-balancing" 372 depends on TREE_RCU 373 default n 374 help 375 This option forces use of the exact RCU_FANOUT value specified, 376 regardless of imbalances in the hierarchy. This is useful for 377 testing RCU itself, and might one day be useful on systems with 378 strong NUMA behavior. 379 380 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 381 382 Say N if unsure. 383 384config TREE_RCU_TRACE 385 def_bool RCU_TRACE && TREE_RCU 386 select DEBUG_FS 387 help 388 This option provides tracing for the TREE_RCU implementation, 389 permitting Makefile to trivially select kernel/rcutree_trace.c. 390 391config PREEMPT_RCU_TRACE 392 def_bool RCU_TRACE && PREEMPT_RCU 393 select DEBUG_FS 394 help 395 This option provides tracing for the PREEMPT_RCU implementation, 396 permitting Makefile to trivially select kernel/rcupreempt_trace.c. 397 398endmenu # "RCU Subsystem" 399 400config IKCONFIG 401 tristate "Kernel .config support" 402 ---help--- 403 This option enables the complete Linux kernel ".config" file 404 contents to be saved in the kernel. It provides documentation 405 of which kernel options are used in a running kernel or in an 406 on-disk kernel. This information can be extracted from the kernel 407 image file with the script scripts/extract-ikconfig and used as 408 input to rebuild the current kernel or to build another kernel. 409 It can also be extracted from a running kernel by reading 410 /proc/config.gz if enabled (below). 411 412config IKCONFIG_PROC 413 bool "Enable access to .config through /proc/config.gz" 414 depends on IKCONFIG && PROC_FS 415 ---help--- 416 This option enables access to the kernel configuration file 417 through /proc/config.gz. 418 419config LOG_BUF_SHIFT 420 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 421 range 12 21 422 default 17 423 help 424 Select kernel log buffer size as a power of 2. 425 Examples: 426 17 => 128 KB 427 16 => 64 KB 428 15 => 32 KB 429 14 => 16 KB 430 13 => 8 KB 431 12 => 4 KB 432 433# 434# Architectures with an unreliable sched_clock() should select this: 435# 436config HAVE_UNSTABLE_SCHED_CLOCK 437 bool 438 439config GROUP_SCHED 440 bool "Group CPU scheduler" 441 depends on EXPERIMENTAL 442 default n 443 help 444 This feature lets CPU scheduler recognize task groups and control CPU 445 bandwidth allocation to such task groups. 446 In order to create a group from arbitrary set of processes, use 447 CONFIG_CGROUPS. (See Control Group support.) 448 449config FAIR_GROUP_SCHED 450 bool "Group scheduling for SCHED_OTHER" 451 depends on GROUP_SCHED 452 default GROUP_SCHED 453 454config RT_GROUP_SCHED 455 bool "Group scheduling for SCHED_RR/FIFO" 456 depends on EXPERIMENTAL 457 depends on GROUP_SCHED 458 default n 459 help 460 This feature lets you explicitly allocate real CPU bandwidth 461 to users or control groups (depending on the "Basis for grouping tasks" 462 setting below. If enabled, it will also make it impossible to 463 schedule realtime tasks for non-root users until you allocate 464 realtime bandwidth for them. 465 See Documentation/scheduler/sched-rt-group.txt for more information. 466 467choice 468 depends on GROUP_SCHED 469 prompt "Basis for grouping tasks" 470 default USER_SCHED 471 472config USER_SCHED 473 bool "user id" 474 help 475 This option will choose userid as the basis for grouping 476 tasks, thus providing equal CPU bandwidth to each user. 477 478config CGROUP_SCHED 479 bool "Control groups" 480 depends on CGROUPS 481 help 482 This option allows you to create arbitrary task groups 483 using the "cgroup" pseudo filesystem and control 484 the cpu bandwidth allocated to each such task group. 485 Refer to Documentation/cgroups/cgroups.txt for more 486 information on "cgroup" pseudo filesystem. 487 488endchoice 489 490menuconfig CGROUPS 491 boolean "Control Group support" 492 help 493 This option adds support for grouping sets of processes together, for 494 use with process control subsystems such as Cpusets, CFS, memory 495 controls or device isolation. 496 See 497 - Documentation/scheduler/sched-design-CFS.txt (CFS) 498 - Documentation/cgroups/ (features for grouping, isolation 499 and resource control) 500 501 Say N if unsure. 502 503if CGROUPS 504 505config CGROUP_DEBUG 506 bool "Example debug cgroup subsystem" 507 depends on CGROUPS 508 default n 509 help 510 This option enables a simple cgroup subsystem that 511 exports useful debugging information about the cgroups 512 framework. 513 514 Say N if unsure. 515 516config CGROUP_NS 517 bool "Namespace cgroup subsystem" 518 depends on CGROUPS 519 help 520 Provides a simple namespace cgroup subsystem to 521 provide hierarchical naming of sets of namespaces, 522 for instance virtual servers and checkpoint/restart 523 jobs. 524 525config CGROUP_FREEZER 526 bool "Freezer cgroup subsystem" 527 depends on CGROUPS 528 help 529 Provides a way to freeze and unfreeze all tasks in a 530 cgroup. 531 532config CGROUP_DEVICE 533 bool "Device controller for cgroups" 534 depends on CGROUPS && EXPERIMENTAL 535 help 536 Provides a cgroup implementing whitelists for devices which 537 a process in the cgroup can mknod or open. 538 539config CPUSETS 540 bool "Cpuset support" 541 depends on CGROUPS 542 help 543 This option will let you create and manage CPUSETs which 544 allow dynamically partitioning a system into sets of CPUs and 545 Memory Nodes and assigning tasks to run only within those sets. 546 This is primarily useful on large SMP or NUMA systems. 547 548 Say N if unsure. 549 550config PROC_PID_CPUSET 551 bool "Include legacy /proc/<pid>/cpuset file" 552 depends on CPUSETS 553 default y 554 555config CGROUP_CPUACCT 556 bool "Simple CPU accounting cgroup subsystem" 557 depends on CGROUPS 558 help 559 Provides a simple Resource Controller for monitoring the 560 total CPU consumed by the tasks in a cgroup. 561 562config RESOURCE_COUNTERS 563 bool "Resource counters" 564 help 565 This option enables controller independent resource accounting 566 infrastructure that works with cgroups. 567 depends on CGROUPS 568 569config CGROUP_MEM_RES_CTLR 570 bool "Memory Resource Controller for Control Groups" 571 depends on CGROUPS && RESOURCE_COUNTERS 572 select MM_OWNER 573 help 574 Provides a memory resource controller that manages both anonymous 575 memory and page cache. (See Documentation/cgroups/memory.txt) 576 577 Note that setting this option increases fixed memory overhead 578 associated with each page of memory in the system. By this, 579 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 580 usage tracking struct at boot. Total amount of this is printed out 581 at boot. 582 583 Only enable when you're ok with these trade offs and really 584 sure you need the memory resource controller. Even when you enable 585 this, you can set "cgroup_disable=memory" at your boot option to 586 disable memory resource controller and you can avoid overheads. 587 (and lose benefits of memory resource controller) 588 589 This config option also selects MM_OWNER config option, which 590 could in turn add some fork/exit overhead. 591 592config CGROUP_MEM_RES_CTLR_SWAP 593 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)" 594 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL 595 help 596 Add swap management feature to memory resource controller. When you 597 enable this, you can limit mem+swap usage per cgroup. In other words, 598 when you disable this, memory resource controller has no cares to 599 usage of swap...a process can exhaust all of the swap. This extension 600 is useful when you want to avoid exhaustion swap but this itself 601 adds more overheads and consumes memory for remembering information. 602 Especially if you use 32bit system or small memory system, please 603 be careful about enabling this. When memory resource controller 604 is disabled by boot option, this will be automatically disabled and 605 there will be no overhead from this. Even when you set this config=y, 606 if boot option "noswapaccount" is set, swap will not be accounted. 607 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 608 size is 4096bytes, 512k per 1Gbytes of swap. 609 610endif # CGROUPS 611 612config MM_OWNER 613 bool 614 615config SYSFS_DEPRECATED 616 bool 617 618config SYSFS_DEPRECATED_V2 619 bool "Create deprecated sysfs layout for older userspace tools" 620 depends on SYSFS 621 default y 622 select SYSFS_DEPRECATED 623 help 624 This option switches the layout of sysfs to the deprecated 625 version. 626 627 The current sysfs layout features a unified device tree at 628 /sys/devices/, which is able to express a hierarchy between 629 class devices. If the deprecated option is set to Y, the 630 unified device tree is split into a bus device tree at 631 /sys/devices/ and several individual class device trees at 632 /sys/class/. The class and bus devices will be connected by 633 "<subsystem>:<name>" and the "device" links. The "block" 634 class devices, will not show up in /sys/class/block/. Some 635 subsystems will suppress the creation of some devices which 636 depend on the unified device tree. 637 638 This option is not a pure compatibility option that can 639 be safely enabled on newer distributions. It will change the 640 layout of sysfs to the non-extensible deprecated version, 641 and disable some features, which can not be exported without 642 confusing older userspace tools. Since 2007/2008 all major 643 distributions do not enable this option, and ship no tools which 644 depend on the deprecated layout or this option. 645 646 If you are using a new kernel on an older distribution, or use 647 older userspace tools, you might need to say Y here. Do not say Y, 648 if the original kernel, that came with your distribution, has 649 this option set to N. 650 651config RELAY 652 bool "Kernel->user space relay support (formerly relayfs)" 653 help 654 This option enables support for relay interface support in 655 certain file systems (such as debugfs). 656 It is designed to provide an efficient mechanism for tools and 657 facilities to relay large amounts of data from kernel space to 658 user space. 659 660 If unsure, say N. 661 662config NAMESPACES 663 bool "Namespaces support" if EMBEDDED 664 default !EMBEDDED 665 help 666 Provides the way to make tasks work with different objects using 667 the same id. For example same IPC id may refer to different objects 668 or same user id or pid may refer to different tasks when used in 669 different namespaces. 670 671config UTS_NS 672 bool "UTS namespace" 673 depends on NAMESPACES 674 help 675 In this namespace tasks see different info provided with the 676 uname() system call 677 678config IPC_NS 679 bool "IPC namespace" 680 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE) 681 help 682 In this namespace tasks work with IPC ids which correspond to 683 different IPC objects in different namespaces. 684 685config USER_NS 686 bool "User namespace (EXPERIMENTAL)" 687 depends on NAMESPACES && EXPERIMENTAL 688 help 689 This allows containers, i.e. vservers, to use user namespaces 690 to provide different user info for different servers. 691 If unsure, say N. 692 693config PID_NS 694 bool "PID Namespaces (EXPERIMENTAL)" 695 default n 696 depends on NAMESPACES && EXPERIMENTAL 697 help 698 Support process id namespaces. This allows having multiple 699 processes with the same pid as long as they are in different 700 pid namespaces. This is a building block of containers. 701 702 Unless you want to work with an experimental feature 703 say N here. 704 705config NET_NS 706 bool "Network namespace" 707 default n 708 depends on NAMESPACES && EXPERIMENTAL && NET 709 help 710 Allow user space to create what appear to be multiple instances 711 of the network stack. 712 713config BLK_DEV_INITRD 714 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 715 depends on BROKEN || !FRV 716 help 717 The initial RAM filesystem is a ramfs which is loaded by the 718 boot loader (loadlin or lilo) and that is mounted as root 719 before the normal boot procedure. It is typically used to 720 load modules needed to mount the "real" root file system, 721 etc. See <file:Documentation/initrd.txt> for details. 722 723 If RAM disk support (BLK_DEV_RAM) is also included, this 724 also enables initial RAM disk (initrd) support and adds 725 15 Kbytes (more on some other architectures) to the kernel size. 726 727 If unsure say Y. 728 729if BLK_DEV_INITRD 730 731source "usr/Kconfig" 732 733endif 734 735config CC_OPTIMIZE_FOR_SIZE 736 bool "Optimize for size" 737 default y 738 help 739 Enabling this option will pass "-Os" instead of "-O2" to gcc 740 resulting in a smaller kernel. 741 742 If unsure, say Y. 743 744config SYSCTL 745 bool 746 747config ANON_INODES 748 bool 749 750menuconfig EMBEDDED 751 bool "Configure standard kernel features (for small systems)" 752 help 753 This option allows certain base kernel options and settings 754 to be disabled or tweaked. This is for specialized 755 environments which can tolerate a "non-standard" kernel. 756 Only use this if you really know what you are doing. 757 758config UID16 759 bool "Enable 16-bit UID system calls" if EMBEDDED 760 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) 761 default y 762 help 763 This enables the legacy 16-bit UID syscall wrappers. 764 765config SYSCTL_SYSCALL 766 bool "Sysctl syscall support" if EMBEDDED 767 default y 768 select SYSCTL 769 ---help--- 770 sys_sysctl uses binary paths that have been found challenging 771 to properly maintain and use. The interface in /proc/sys 772 using paths with ascii names is now the primary path to this 773 information. 774 775 Almost nothing using the binary sysctl interface so if you are 776 trying to save some space it is probably safe to disable this, 777 making your kernel marginally smaller. 778 779 If unsure say Y here. 780 781config KALLSYMS 782 bool "Load all symbols for debugging/ksymoops" if EMBEDDED 783 default y 784 help 785 Say Y here to let the kernel print out symbolic crash information and 786 symbolic stack backtraces. This increases the size of the kernel 787 somewhat, as all symbols have to be loaded into the kernel image. 788 789config KALLSYMS_ALL 790 bool "Include all symbols in kallsyms" 791 depends on DEBUG_KERNEL && KALLSYMS 792 help 793 Normally kallsyms only contains the symbols of functions, for nicer 794 OOPS messages. Some debuggers can use kallsyms for other 795 symbols too: say Y here to include all symbols, if you need them 796 and you don't care about adding 300k to the size of your kernel. 797 798 Say N. 799 800config KALLSYMS_EXTRA_PASS 801 bool "Do an extra kallsyms pass" 802 depends on KALLSYMS 803 help 804 If kallsyms is not working correctly, the build will fail with 805 inconsistent kallsyms data. If that occurs, log a bug report and 806 turn on KALLSYMS_EXTRA_PASS which should result in a stable build. 807 Always say N here unless you find a bug in kallsyms, which must be 808 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while 809 you wait for kallsyms to be fixed. 810 811 812config HOTPLUG 813 bool "Support for hot-pluggable devices" if EMBEDDED 814 default y 815 help 816 This option is provided for the case where no hotplug or uevent 817 capabilities is wanted by the kernel. You should only consider 818 disabling this option for embedded systems that do not use modules, a 819 dynamic /dev tree, or dynamic device discovery. Just say Y. 820 821config PRINTK 822 default y 823 bool "Enable support for printk" if EMBEDDED 824 help 825 This option enables normal printk support. Removing it 826 eliminates most of the message strings from the kernel image 827 and makes the kernel more or less silent. As this makes it 828 very difficult to diagnose system problems, saying N here is 829 strongly discouraged. 830 831config BUG 832 bool "BUG() support" if EMBEDDED 833 default y 834 help 835 Disabling this option eliminates support for BUG and WARN, reducing 836 the size of your kernel image and potentially quietly ignoring 837 numerous fatal conditions. You should only consider disabling this 838 option for embedded systems with no facilities for reporting errors. 839 Just say Y. 840 841config ELF_CORE 842 default y 843 bool "Enable ELF core dumps" if EMBEDDED 844 help 845 Enable support for generating core dumps. Disabling saves about 4k. 846 847config PCSPKR_PLATFORM 848 bool "Enable PC-Speaker support" if EMBEDDED 849 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES 850 default y 851 help 852 This option allows to disable the internal PC-Speaker 853 support, saving some memory. 854 855config BASE_FULL 856 default y 857 bool "Enable full-sized data structures for core" if EMBEDDED 858 help 859 Disabling this option reduces the size of miscellaneous core 860 kernel data structures. This saves memory on small machines, 861 but may reduce performance. 862 863config FUTEX 864 bool "Enable futex support" if EMBEDDED 865 default y 866 select RT_MUTEXES 867 help 868 Disabling this option will cause the kernel to be built without 869 support for "fast userspace mutexes". The resulting kernel may not 870 run glibc-based applications correctly. 871 872config EPOLL 873 bool "Enable eventpoll support" if EMBEDDED 874 default y 875 select ANON_INODES 876 help 877 Disabling this option will cause the kernel to be built without 878 support for epoll family of system calls. 879 880config SIGNALFD 881 bool "Enable signalfd() system call" if EMBEDDED 882 select ANON_INODES 883 default y 884 help 885 Enable the signalfd() system call that allows to receive signals 886 on a file descriptor. 887 888 If unsure, say Y. 889 890config TIMERFD 891 bool "Enable timerfd() system call" if EMBEDDED 892 select ANON_INODES 893 default y 894 help 895 Enable the timerfd() system call that allows to receive timer 896 events on a file descriptor. 897 898 If unsure, say Y. 899 900config EVENTFD 901 bool "Enable eventfd() system call" if EMBEDDED 902 select ANON_INODES 903 default y 904 help 905 Enable the eventfd() system call that allows to receive both 906 kernel notification (ie. KAIO) or userspace notifications. 907 908 If unsure, say Y. 909 910config SHMEM 911 bool "Use full shmem filesystem" if EMBEDDED 912 default y 913 depends on MMU 914 help 915 The shmem is an internal filesystem used to manage shared memory. 916 It is backed by swap and manages resource limits. It is also exported 917 to userspace as tmpfs if TMPFS is enabled. Disabling this 918 option replaces shmem and tmpfs with the much simpler ramfs code, 919 which may be appropriate on small systems without swap. 920 921config AIO 922 bool "Enable AIO support" if EMBEDDED 923 default y 924 help 925 This option enables POSIX asynchronous I/O which may by used 926 by some high performance threaded applications. Disabling 927 this option saves about 7k. 928 929config HAVE_PERF_COUNTERS 930 bool 931 help 932 See tools/perf/design.txt for details. 933 934menu "Performance Counters" 935 936config PERF_COUNTERS 937 bool "Kernel Performance Counters" 938 depends on HAVE_PERF_COUNTERS 939 select ANON_INODES 940 help 941 Enable kernel support for performance counter hardware. 942 943 Performance counters are special hardware registers available 944 on most modern CPUs. These registers count the number of certain 945 types of hw events: such as instructions executed, cachemisses 946 suffered, or branches mis-predicted - without slowing down the 947 kernel or applications. These registers can also trigger interrupts 948 when a threshold number of events have passed - and can thus be 949 used to profile the code that runs on that CPU. 950 951 The Linux Performance Counter subsystem provides an abstraction of 952 these hardware capabilities, available via a system call. It 953 provides per task and per CPU counters, and it provides event 954 capabilities on top of those. 955 956 Say Y if unsure. 957 958config EVENT_PROFILE 959 bool "Tracepoint profile sources" 960 depends on PERF_COUNTERS && EVENT_TRACER 961 default y 962 963endmenu 964 965config VM_EVENT_COUNTERS 966 default y 967 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED 968 help 969 VM event counters are needed for event counts to be shown. 970 This option allows the disabling of the VM event counters 971 on EMBEDDED systems. /proc/vmstat will only show page counts 972 if VM event counters are disabled. 973 974config PCI_QUIRKS 975 default y 976 bool "Enable PCI quirk workarounds" if EMBEDDED 977 depends on PCI 978 help 979 This enables workarounds for various PCI chipset 980 bugs/quirks. Disable this only if your target machine is 981 unaffected by PCI quirks. 982 983config SLUB_DEBUG 984 default y 985 bool "Enable SLUB debugging support" if EMBEDDED 986 depends on SLUB && SYSFS 987 help 988 SLUB has extensive debug support features. Disabling these can 989 result in significant savings in code size. This also disables 990 SLUB sysfs support. /sys/slab will not exist and there will be 991 no support for cache validation etc. 992 993config STRIP_ASM_SYMS 994 bool "Strip assembler-generated symbols during link" 995 default n 996 help 997 Strip internal assembler-generated symbols during a link (symbols 998 that look like '.Lxxx') so they don't pollute the output of 999 get_wchan() and suchlike. 1000 1001config COMPAT_BRK 1002 bool "Disable heap randomization" 1003 default y 1004 help 1005 Randomizing heap placement makes heap exploits harder, but it 1006 also breaks ancient binaries (including anything libc5 based). 1007 This option changes the bootup default to heap randomization 1008 disabled, and can be overridden at runtime by setting 1009 /proc/sys/kernel/randomize_va_space to 2. 1010 1011 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1012 1013choice 1014 prompt "Choose SLAB allocator" 1015 default SLUB 1016 help 1017 This option allows to select a slab allocator. 1018 1019config SLAB 1020 bool "SLAB" 1021 help 1022 The regular slab allocator that is established and known to work 1023 well in all environments. It organizes cache hot objects in 1024 per cpu and per node queues. 1025 1026config SLUB 1027 bool "SLUB (Unqueued Allocator)" 1028 help 1029 SLUB is a slab allocator that minimizes cache line usage 1030 instead of managing queues of cached objects (SLAB approach). 1031 Per cpu caching is realized using slabs of objects instead 1032 of queues of objects. SLUB can use memory efficiently 1033 and has enhanced diagnostics. SLUB is the default choice for 1034 a slab allocator. 1035 1036config SLOB 1037 depends on EMBEDDED 1038 bool "SLOB (Simple Allocator)" 1039 help 1040 SLOB replaces the stock allocator with a drastically simpler 1041 allocator. SLOB is generally more space efficient but 1042 does not perform as well on large systems. 1043 1044endchoice 1045 1046config PROFILING 1047 bool "Profiling support (EXPERIMENTAL)" 1048 help 1049 Say Y here to enable the extended profiling support mechanisms used 1050 by profilers such as OProfile. 1051 1052# 1053# Place an empty function call at each tracepoint site. Can be 1054# dynamically changed for a probe function. 1055# 1056config TRACEPOINTS 1057 bool 1058 1059config MARKERS 1060 bool "Activate markers" 1061 select TRACEPOINTS 1062 help 1063 Place an empty function call at each marker site. Can be 1064 dynamically changed for a probe function. 1065 1066source "arch/Kconfig" 1067 1068config SLOW_WORK 1069 default n 1070 bool 1071 help 1072 The slow work thread pool provides a number of dynamically allocated 1073 threads that can be used by the kernel to perform operations that 1074 take a relatively long time. 1075 1076 An example of this would be CacheFiles doing a path lookup followed 1077 by a series of mkdirs and a create call, all of which have to touch 1078 disk. 1079 1080 See Documentation/slow-work.txt. 1081 1082endmenu # General setup 1083 1084config HAVE_GENERIC_DMA_COHERENT 1085 bool 1086 default n 1087 1088config SLABINFO 1089 bool 1090 depends on PROC_FS 1091 depends on SLAB || SLUB_DEBUG 1092 default y 1093 1094config RT_MUTEXES 1095 boolean 1096 1097config BASE_SMALL 1098 int 1099 default 0 if BASE_FULL 1100 default 1 if !BASE_FULL 1101 1102menuconfig MODULES 1103 bool "Enable loadable module support" 1104 help 1105 Kernel modules are small pieces of compiled code which can 1106 be inserted in the running kernel, rather than being 1107 permanently built into the kernel. You use the "modprobe" 1108 tool to add (and sometimes remove) them. If you say Y here, 1109 many parts of the kernel can be built as modules (by 1110 answering M instead of Y where indicated): this is most 1111 useful for infrequently used options which are not required 1112 for booting. For more information, see the man pages for 1113 modprobe, lsmod, modinfo, insmod and rmmod. 1114 1115 If you say Y here, you will need to run "make 1116 modules_install" to put the modules under /lib/modules/ 1117 where modprobe can find them (you may need to be root to do 1118 this). 1119 1120 If unsure, say Y. 1121 1122if MODULES 1123 1124config MODULE_FORCE_LOAD 1125 bool "Forced module loading" 1126 default n 1127 help 1128 Allow loading of modules without version information (ie. modprobe 1129 --force). Forced module loading sets the 'F' (forced) taint flag and 1130 is usually a really bad idea. 1131 1132config MODULE_UNLOAD 1133 bool "Module unloading" 1134 help 1135 Without this option you will not be able to unload any 1136 modules (note that some modules may not be unloadable 1137 anyway), which makes your kernel smaller, faster 1138 and simpler. If unsure, say Y. 1139 1140config MODULE_FORCE_UNLOAD 1141 bool "Forced module unloading" 1142 depends on MODULE_UNLOAD && EXPERIMENTAL 1143 help 1144 This option allows you to force a module to unload, even if the 1145 kernel believes it is unsafe: the kernel will remove the module 1146 without waiting for anyone to stop using it (using the -f option to 1147 rmmod). This is mainly for kernel developers and desperate users. 1148 If unsure, say N. 1149 1150config MODVERSIONS 1151 bool "Module versioning support" 1152 help 1153 Usually, you have to use modules compiled with your kernel. 1154 Saying Y here makes it sometimes possible to use modules 1155 compiled for different kernels, by adding enough information 1156 to the modules to (hopefully) spot any changes which would 1157 make them incompatible with the kernel you are running. If 1158 unsure, say N. 1159 1160config MODULE_SRCVERSION_ALL 1161 bool "Source checksum for all modules" 1162 help 1163 Modules which contain a MODULE_VERSION get an extra "srcversion" 1164 field inserted into their modinfo section, which contains a 1165 sum of the source files which made it. This helps maintainers 1166 see exactly which source was used to build a module (since 1167 others sometimes change the module source without updating 1168 the version). With this option, such a "srcversion" field 1169 will be created for all modules. If unsure, say N. 1170 1171endif # MODULES 1172 1173config INIT_ALL_POSSIBLE 1174 bool 1175 help 1176 Back when each arch used to define their own cpu_online_map and 1177 cpu_possible_map, some of them chose to initialize cpu_possible_map 1178 with all 1s, and others with all 0s. When they were centralised, 1179 it was better to provide this option than to break all the archs 1180 and have several arch maintainers pursuing me down dark alleys. 1181 1182config STOP_MACHINE 1183 bool 1184 default y 1185 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1186 help 1187 Need stop_machine() primitive. 1188 1189source "block/Kconfig" 1190 1191config PREEMPT_NOTIFIERS 1192 bool 1193 1194