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 These are 47 drivers that have been replaced by something else, and/or are 48 scheduled to be removed in a future kernel release. 49 50 Unless you intend to help test and develop a feature or driver that 51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