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diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt new file mode 100644 index 00000000..db3b1aba --- /dev/null +++ b/Documentation/filesystems/proc.txt @@ -0,0 +1,1544 @@ +------------------------------------------------------------------------------ + T H E /proc F I L E S Y S T E M +------------------------------------------------------------------------------ +/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 + Bodo Bauer <bb@ricochet.net> + +2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 +move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 +------------------------------------------------------------------------------ +Version 1.3 Kernel version 2.2.12 + Kernel version 2.4.0-test11-pre4 +------------------------------------------------------------------------------ +fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 + +Table of Contents +----------------- + + 0 Preface + 0.1 Introduction/Credits + 0.2 Legal Stuff + + 1 Collecting System Information + 1.1 Process-Specific Subdirectories + 1.2 Kernel data + 1.3 IDE devices in /proc/ide + 1.4 Networking info in /proc/net + 1.5 SCSI info + 1.6 Parallel port info in /proc/parport + 1.7 TTY info in /proc/tty + 1.8 Miscellaneous kernel statistics in /proc/stat + 1.9 Ext4 file system parameters + + 2 Modifying System Parameters + + 3 Per-Process Parameters + 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer + score + 3.2 /proc/<pid>/oom_score - Display current oom-killer score + 3.3 /proc/<pid>/io - Display the IO accounting fields + 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings + 3.5 /proc/<pid>/mountinfo - Information about mounts + 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm + + +------------------------------------------------------------------------------ +Preface +------------------------------------------------------------------------------ + +0.1 Introduction/Credits +------------------------ + +This documentation is part of a soon (or so we hope) to be released book on +the SuSE Linux distribution. As there is no complete documentation for the +/proc file system and we've used many freely available sources to write these +chapters, it seems only fair to give the work back to the Linux community. +This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm +afraid it's still far from complete, but we hope it will be useful. As far as +we know, it is the first 'all-in-one' document about the /proc file system. It +is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, +SPARC, AXP, etc., features, you probably won't find what you are looking for. +It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But +additions and patches are welcome and will be added to this document if you +mail them to Bodo. + +We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of +other people for help compiling this documentation. We'd also like to extend a +special thank you to Andi Kleen for documentation, which we relied on heavily +to create this document, as well as the additional information he provided. +Thanks to everybody else who contributed source or docs to the Linux kernel +and helped create a great piece of software... :) + +If you have any comments, corrections or additions, please don't hesitate to +contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this +document. + +The latest version of this document is available online at +http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html + +If the above direction does not works for you, you could try the kernel +mailing list at linux-kernel@vger.kernel.org and/or try to reach me at +comandante@zaralinux.com. + +0.2 Legal Stuff +--------------- + +We don't guarantee the correctness of this document, and if you come to us +complaining about how you screwed up your system because of incorrect +documentation, we won't feel responsible... + +------------------------------------------------------------------------------ +CHAPTER 1: COLLECTING SYSTEM INFORMATION +------------------------------------------------------------------------------ + +------------------------------------------------------------------------------ +In This Chapter +------------------------------------------------------------------------------ +* Investigating the properties of the pseudo file system /proc and its + ability to provide information on the running Linux system +* Examining /proc's structure +* Uncovering various information about the kernel and the processes running + on the system +------------------------------------------------------------------------------ + + +The proc file system acts as an interface to internal data structures in the +kernel. It can be used to obtain information about the system and to change +certain kernel parameters at runtime (sysctl). + +First, we'll take a look at the read-only parts of /proc. In Chapter 2, we +show you how you can use /proc/sys to change settings. + +1.1 Process-Specific Subdirectories +----------------------------------- + +The directory /proc contains (among other things) one subdirectory for each +process running on the system, which is named after the process ID (PID). + +The link self points to the process reading the file system. Each process +subdirectory has the entries listed in Table 1-1. + + +Table 1-1: Process specific entries in /proc +.............................................................................. + File Content + clear_refs Clears page referenced bits shown in smaps output + cmdline Command line arguments + cpu Current and last cpu in which it was executed (2.4)(smp) + cwd Link to the current working directory + environ Values of environment variables + exe Link to the executable of this process + fd Directory, which contains all file descriptors + maps Memory maps to executables and library files (2.4) + mem Memory held by this process + root Link to the root directory of this process + stat Process status + statm Process memory status information + status Process status in human readable form + wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan + pagemap Page table + stack Report full stack trace, enable via CONFIG_STACKTRACE + smaps a extension based on maps, showing the memory consumption of + each mapping +.............................................................................. + +For example, to get the status information of a process, all you have to do is +read the file /proc/PID/status: + + >cat /proc/self/status + Name: cat + State: R (running) + Tgid: 5452 + Pid: 5452 + PPid: 743 + TracerPid: 0 (2.4) + Uid: 501 501 501 501 + Gid: 100 100 100 100 + FDSize: 256 + Groups: 100 14 16 + VmPeak: 5004 kB + VmSize: 5004 kB + VmLck: 0 kB + VmHWM: 476 kB + VmRSS: 476 kB + VmData: 156 kB + VmStk: 88 kB + VmExe: 68 kB + VmLib: 1412 kB + VmPTE: 20 kb + VmSwap: 0 kB + Threads: 1 + SigQ: 0/28578 + SigPnd: 0000000000000000 + ShdPnd: 0000000000000000 + SigBlk: 0000000000000000 + SigIgn: 0000000000000000 + SigCgt: 0000000000000000 + CapInh: 00000000fffffeff + CapPrm: 0000000000000000 + CapEff: 0000000000000000 + CapBnd: ffffffffffffffff + voluntary_ctxt_switches: 0 + nonvoluntary_ctxt_switches: 1 + +This shows you nearly the same information you would get if you viewed it with +the ps command. In fact, ps uses the proc file system to obtain its +information. But you get a more detailed view of the process by reading the +file /proc/PID/status. It fields are described in table 1-2. + +The statm file contains more detailed information about the process +memory usage. Its seven fields are explained in Table 1-3. The stat file +contains details information about the process itself. Its fields are +explained in Table 1-4. + +(for SMP CONFIG users) +For making accounting scalable, RSS related information are handled in +asynchronous manner and the vaule may not be very precise. To see a precise +snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. +It's slow but very precise. + +Table 1-2: Contents of the status files (as of 2.6.30-rc7) +.............................................................................. + Field Content + Name filename of the executable + State state (R is running, S is sleeping, D is sleeping + in an uninterruptible wait, Z is zombie, + T is traced or stopped) + Tgid thread group ID + Pid process id + PPid process id of the parent process + TracerPid PID of process tracing this process (0 if not) + Uid Real, effective, saved set, and file system UIDs + Gid Real, effective, saved set, and file system GIDs + FDSize number of file descriptor slots currently allocated + Groups supplementary group list + VmPeak peak virtual memory size + VmSize total program size + VmLck locked memory size + VmHWM peak resident set size ("high water mark") + VmRSS size of memory portions + VmData size of data, stack, and text segments + VmStk size of data, stack, and text segments + VmExe size of text segment + VmLib size of shared library code + VmPTE size of page table entries + VmSwap size of swap usage (the number of referred swapents) + Threads number of threads + SigQ number of signals queued/max. number for queue + SigPnd bitmap of pending signals for the thread + ShdPnd bitmap of shared pending signals for the process + SigBlk bitmap of blocked signals + SigIgn bitmap of ignored signals + SigCgt bitmap of catched signals + CapInh bitmap of inheritable capabilities + CapPrm bitmap of permitted capabilities + CapEff bitmap of effective capabilities + CapBnd bitmap of capabilities bounding set + Cpus_allowed mask of CPUs on which this process may run + Cpus_allowed_list Same as previous, but in "list format" + Mems_allowed mask of memory nodes allowed to this process + Mems_allowed_list Same as previous, but in "list format" + voluntary_ctxt_switches number of voluntary context switches + nonvoluntary_ctxt_switches number of non voluntary context switches +.............................................................................. + +Table 1-3: Contents of the statm files (as of 2.6.8-rc3) +.............................................................................. + Field Content + size total program size (pages) (same as VmSize in status) + resident size of memory portions (pages) (same as VmRSS in status) + shared number of pages that are shared (i.e. backed by a file) + trs number of pages that are 'code' (not including libs; broken, + includes data segment) + lrs number of pages of library (always 0 on 2.6) + drs number of pages of data/stack (including libs; broken, + includes library text) + dt number of dirty pages (always 0 on 2.6) +.............................................................................. + + +Table 1-4: Contents of the stat files (as of 2.6.30-rc7) +.............................................................................. + Field Content + pid process id + tcomm filename of the executable + state state (R is running, S is sleeping, D is sleeping in an + uninterruptible wait, Z is zombie, T is traced or stopped) + ppid process id of the parent process + pgrp pgrp of the process + sid session id + tty_nr tty the process uses + tty_pgrp pgrp of the tty + flags task flags + min_flt number of minor faults + cmin_flt number of minor faults with child's + maj_flt number of major faults + cmaj_flt number of major faults with child's + utime user mode jiffies + stime kernel mode jiffies + cutime user mode jiffies with child's + cstime kernel mode jiffies with child's + priority priority level + nice nice level + num_threads number of threads + it_real_value (obsolete, always 0) + start_time time the process started after system boot + vsize virtual memory size + rss resident set memory size + rsslim current limit in bytes on the rss + start_code address above which program text can run + end_code address below which program text can run + start_stack address of the start of the stack + esp current value of ESP + eip current value of EIP + pending bitmap of pending signals + blocked bitmap of blocked signals + sigign bitmap of ignored signals + sigcatch bitmap of catched signals + wchan address where process went to sleep + 0 (place holder) + 0 (place holder) + exit_signal signal to send to parent thread on exit + task_cpu which CPU the task is scheduled on + rt_priority realtime priority + policy scheduling policy (man sched_setscheduler) + blkio_ticks time spent waiting for block IO + gtime guest time of the task in jiffies + cgtime guest time of the task children in jiffies +.............................................................................. + +The /proc/PID/maps file containing the currently mapped memory regions and +their access permissions. + +The format is: + +address perms offset dev inode pathname + +08048000-08049000 r-xp 00000000 03:00 8312 /opt/test +08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test +0804a000-0806b000 rw-p 00000000 00:00 0 [heap] +a7cb1000-a7cb2000 ---p 00000000 00:00 0 +a7cb2000-a7eb2000 rw-p 00000000 00:00 0 +a7eb2000-a7eb3000 ---p 00000000 00:00 0 +a7eb3000-a7ed5000 rw-p 00000000 00:00 0 +a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 +a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 +a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 +a800b000-a800e000 rw-p 00000000 00:00 0 +a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 +a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 +a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 +a8024000-a8027000 rw-p 00000000 00:00 0 +a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 +a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 +a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 +aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] +ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] + +where "address" is the address space in the process that it occupies, "perms" +is a set of permissions: + + r = read + w = write + x = execute + s = shared + p = private (copy on write) + +"offset" is the offset into the mapping, "dev" is the device (major:minor), and +"inode" is the inode on that device. 0 indicates that no inode is associated +with the memory region, as the case would be with BSS (uninitialized data). +The "pathname" shows the name associated file for this mapping. If the mapping +is not associated with a file: + + [heap] = the heap of the program + [stack] = the stack of the main process + [vdso] = the "virtual dynamic shared object", + the kernel system call handler + + or if empty, the mapping is anonymous. + + +The /proc/PID/smaps is an extension based on maps, showing the memory +consumption for each of the process's mappings. For each of mappings there +is a series of lines such as the following: + +08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash +Size: 1084 kB +Rss: 892 kB +Pss: 374 kB +Shared_Clean: 892 kB +Shared_Dirty: 0 kB +Private_Clean: 0 kB +Private_Dirty: 0 kB +Referenced: 892 kB +Anonymous: 0 kB +Swap: 0 kB +KernelPageSize: 4 kB +MMUPageSize: 4 kB +Locked: 374 kB + +The first of these lines shows the same information as is displayed for the +mapping in /proc/PID/maps. The remaining lines show the size of the mapping +(size), the amount of the mapping that is currently resident in RAM (RSS), the +process' proportional share of this mapping (PSS), the number of clean and +dirty private pages in the mapping. Note that even a page which is part of a +MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used +by only one process, is accounted as private and not as shared. "Referenced" +indicates the amount of memory currently marked as referenced or accessed. +"Anonymous" shows the amount of memory that does not belong to any file. Even +a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE +and a page is modified, the file page is replaced by a private anonymous copy. +"Swap" shows how much would-be-anonymous memory is also used, but out on +swap. + +This file is only present if the CONFIG_MMU kernel configuration option is +enabled. + +The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG +bits on both physical and virtual pages associated with a process. +To clear the bits for all the pages associated with the process + > echo 1 > /proc/PID/clear_refs + +To clear the bits for the anonymous pages associated with the process + > echo 2 > /proc/PID/clear_refs + +To clear the bits for the file mapped pages associated with the process + > echo 3 > /proc/PID/clear_refs +Any other value written to /proc/PID/clear_refs will have no effect. + +The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags +using /proc/kpageflags and number of times a page is mapped using +/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. + +1.2 Kernel data +--------------- + +Similar to the process entries, the kernel data files give information about +the running kernel. The files used to obtain this information are contained in +/proc and are listed in Table 1-5. Not all of these will be present in your +system. It depends on the kernel configuration and the loaded modules, which +files are there, and which are missing. + +Table 1-5: Kernel info in /proc +.............................................................................. + File Content + apm Advanced power management info + buddyinfo Kernel memory allocator information (see text) (2.5) + bus Directory containing bus specific information + cmdline Kernel command line + cpuinfo Info about the CPU + devices Available devices (block and character) + dma Used DMS channels + filesystems Supported filesystems + driver Various drivers grouped here, currently rtc (2.4) + execdomains Execdomains, related to security (2.4) + fb Frame Buffer devices (2.4) + fs File system parameters, currently nfs/exports (2.4) + ide Directory containing info about the IDE subsystem + interrupts Interrupt usage + iomem Memory map (2.4) + ioports I/O port usage + irq Masks for irq to cpu affinity (2.4)(smp?) + isapnp ISA PnP (Plug&Play) Info (2.4) + kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) + kmsg Kernel messages + ksyms Kernel symbol table + loadavg Load average of last 1, 5 & 15 minutes + locks Kernel locks + meminfo Memory info + misc Miscellaneous + modules List of loaded modules + mounts Mounted filesystems + net Networking info (see text) + pagetypeinfo Additional page allocator information (see text) (2.5) + partitions Table of partitions known to the system + pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, + decoupled by lspci (2.4) + rtc Real time clock + scsi SCSI info (see text) + slabinfo Slab pool info + softirqs softirq usage + stat Overall statistics + swaps Swap space utilization + sys See chapter 2 + sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) + tty Info of tty drivers + uptime System uptime + version Kernel version + video bttv info of video resources (2.4) + vmallocinfo Show vmalloced areas +.............................................................................. + +You can, for example, check which interrupts are currently in use and what +they are used for by looking in the file /proc/interrupts: + + > cat /proc/interrupts + CPU0 + 0: 8728810 XT-PIC timer + 1: 895 XT-PIC keyboard + 2: 0 XT-PIC cascade + 3: 531695 XT-PIC aha152x + 4: 2014133 XT-PIC serial + 5: 44401 XT-PIC pcnet_cs + 8: 2 XT-PIC rtc + 11: 8 XT-PIC i82365 + 12: 182918 XT-PIC PS/2 Mouse + 13: 1 XT-PIC fpu + 14: 1232265 XT-PIC ide0 + 15: 7 XT-PIC ide1 + NMI: 0 + +In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the +output of a SMP machine): + + > cat /proc/interrupts + + CPU0 CPU1 + 0: 1243498 1214548 IO-APIC-edge timer + 1: 8949 8958 IO-APIC-edge keyboard + 2: 0 0 XT-PIC cascade + 5: 11286 10161 IO-APIC-edge soundblaster + 8: 1 0 IO-APIC-edge rtc + 9: 27422 27407 IO-APIC-edge 3c503 + 12: 113645 113873 IO-APIC-edge PS/2 Mouse + 13: 0 0 XT-PIC fpu + 14: 22491 24012 IO-APIC-edge ide0 + 15: 2183 2415 IO-APIC-edge ide1 + 17: 30564 30414 IO-APIC-level eth0 + 18: 177 164 IO-APIC-level bttv + NMI: 2457961 2457959 + LOC: 2457882 2457881 + ERR: 2155 + +NMI is incremented in this case because every timer interrupt generates a NMI +(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. + +LOC is the local interrupt counter of the internal APIC of every CPU. + +ERR is incremented in the case of errors in the IO-APIC bus (the bus that +connects the CPUs in a SMP system. This means that an error has been detected, +the IO-APIC automatically retry the transmission, so it should not be a big +problem, but you should read the SMP-FAQ. + +In 2.6.2* /proc/interrupts was expanded again. This time the goal was for +/proc/interrupts to display every IRQ vector in use by the system, not +just those considered 'most important'. The new vectors are: + + THR -- interrupt raised when a machine check threshold counter + (typically counting ECC corrected errors of memory or cache) exceeds + a configurable threshold. Only available on some systems. + + TRM -- a thermal event interrupt occurs when a temperature threshold + has been exceeded for the CPU. This interrupt may also be generated + when the temperature drops back to normal. + + SPU -- a spurious interrupt is some interrupt that was raised then lowered + by some IO device before it could be fully processed by the APIC. Hence + the APIC sees the interrupt but does not know what device it came from. + For this case the APIC will generate the interrupt with a IRQ vector + of 0xff. This might also be generated by chipset bugs. + + RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are + sent from one CPU to another per the needs of the OS. Typically, + their statistics are used by kernel developers and interested users to + determine the occurrence of interrupts of the given type. + +The above IRQ vectors are displayed only when relevant. For example, +the threshold vector does not exist on x86_64 platforms. Others are +suppressed when the system is a uniprocessor. As of this writing, only +i386 and x86_64 platforms support the new IRQ vector displays. + +Of some interest is the introduction of the /proc/irq directory to 2.4. +It could be used to set IRQ to CPU affinity, this means that you can "hook" an +IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the +irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and +prof_cpu_mask. + +For example + > ls /proc/irq/ + 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask + 1 11 13 15 17 19 3 5 7 9 default_smp_affinity + > ls /proc/irq/0/ + smp_affinity + +smp_affinity is a bitmask, in which you can specify which CPUs can handle the +IRQ, you can set it by doing: + + > echo 1 > /proc/irq/10/smp_affinity + +This means that only the first CPU will handle the IRQ, but you can also echo +5 which means that only the first and fourth CPU can handle the IRQ. + +The contents of each smp_affinity file is the same by default: + + > cat /proc/irq/0/smp_affinity + ffffffff + +There is an alternate interface, smp_affinity_list which allows specifying +a cpu range instead of a bitmask: + + > cat /proc/irq/0/smp_affinity_list + 1024-1031 + +The default_smp_affinity mask applies to all non-active IRQs, which are the +IRQs which have not yet been allocated/activated, and hence which lack a +/proc/irq/[0-9]* directory. + +The node file on an SMP system shows the node to which the device using the IRQ +reports itself as being attached. This hardware locality information does not +include information about any possible driver locality preference. + +prof_cpu_mask specifies which CPUs are to be profiled by the system wide +profiler. Default value is ffffffff (all cpus if there are only 32 of them). + +The way IRQs are routed is handled by the IO-APIC, and it's Round Robin +between all the CPUs which are allowed to handle it. As usual the kernel has +more info than you and does a better job than you, so the defaults are the +best choice for almost everyone. [Note this applies only to those IO-APIC's +that support "Round Robin" interrupt distribution.] + +There are three more important subdirectories in /proc: net, scsi, and sys. +The general rule is that the contents, or even the existence of these +directories, depend on your kernel configuration. If SCSI is not enabled, the +directory scsi may not exist. The same is true with the net, which is there +only when networking support is present in the running kernel. + +The slabinfo file gives information about memory usage at the slab level. +Linux uses slab pools for memory management above page level in version 2.2. +Commonly used objects have their own slab pool (such as network buffers, +directory cache, and so on). + +.............................................................................. + +> cat /proc/buddyinfo + +Node 0, zone DMA 0 4 5 4 4 3 ... +Node 0, zone Normal 1 0 0 1 101 8 ... +Node 0, zone HighMem 2 0 0 1 1 0 ... + +External fragmentation is a problem under some workloads, and buddyinfo is a +useful tool for helping diagnose these problems. Buddyinfo will give you a +clue as to how big an area you can safely allocate, or why a previous +allocation failed. + +Each column represents the number of pages of a certain order which are +available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in +ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE +available in ZONE_NORMAL, etc... + +More information relevant to external fragmentation can be found in +pagetypeinfo. + +> cat /proc/pagetypeinfo +Page block order: 9 +Pages per block: 512 + +Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 +Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 +Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 +Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 +Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 +Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 +Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 +Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 +Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 +Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 +Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 + +Number of blocks type Unmovable Reclaimable Movable Reserve Isolate +Node 0, zone DMA 2 0 5 1 0 +Node 0, zone DMA32 41 6 967 2 0 + +Fragmentation avoidance in the kernel works by grouping pages of different +migrate types into the same contiguous regions of memory called page blocks. +A page block is typically the size of the default hugepage size e.g. 2MB on +X86-64. By keeping pages grouped based on their ability to move, the kernel +can reclaim pages within a page block to satisfy a high-order allocation. + +The pagetypinfo begins with information on the size of a page block. It +then gives the same type of information as buddyinfo except broken down +by migrate-type and finishes with details on how many page blocks of each +type exist. + +If min_free_kbytes has been tuned correctly (recommendations made by hugeadm +from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can +make an estimate of the likely number of huge pages that can be allocated +at a given point in time. All the "Movable" blocks should be allocatable +unless memory has been mlock()'d. Some of the Reclaimable blocks should +also be allocatable although a lot of filesystem metadata may have to be +reclaimed to achieve this. + +.............................................................................. + +meminfo: + +Provides information about distribution and utilization of memory. This +varies by architecture and compile options. The following is from a +16GB PIII, which has highmem enabled. You may not have all of these fields. + +> cat /proc/meminfo + +The "Locked" indicates whether the mapping is locked in memory or not. + + +MemTotal: 16344972 kB +MemFree: 13634064 kB +Buffers: 3656 kB +Cached: 1195708 kB +SwapCached: 0 kB +Active: 891636 kB +Inactive: 1077224 kB +HighTotal: 15597528 kB +HighFree: 13629632 kB +LowTotal: 747444 kB +LowFree: 4432 kB +SwapTotal: 0 kB +SwapFree: 0 kB +Dirty: 968 kB +Writeback: 0 kB +AnonPages: 861800 kB +Mapped: 280372 kB +Slab: 284364 kB +SReclaimable: 159856 kB +SUnreclaim: 124508 kB +PageTables: 24448 kB +NFS_Unstable: 0 kB +Bounce: 0 kB +WritebackTmp: 0 kB +CommitLimit: 7669796 kB +Committed_AS: 100056 kB +VmallocTotal: 112216 kB +VmallocUsed: 428 kB +VmallocChunk: 111088 kB + + MemTotal: Total usable ram (i.e. physical ram minus a few reserved + bits and the kernel binary code) + MemFree: The sum of LowFree+HighFree + Buffers: Relatively temporary storage for raw disk blocks + shouldn't get tremendously large (20MB or so) + Cached: in-memory cache for files read from the disk (the + pagecache). Doesn't include SwapCached + SwapCached: Memory that once was swapped out, is swapped back in but + still also is in the swapfile (if memory is needed it + doesn't need to be swapped out AGAIN because it is already + in the swapfile. This saves I/O) + Active: Memory that has been used more recently and usually not + reclaimed unless absolutely necessary. + Inactive: Memory which has been less recently used. It is more + eligible to be reclaimed for other purposes + HighTotal: + HighFree: Highmem is all memory above ~860MB of physical memory + Highmem areas are for use by userspace programs, or + for the pagecache. The kernel must use tricks to access + this memory, making it slower to access than lowmem. + LowTotal: + LowFree: Lowmem is memory which can be used for everything that + highmem can be used for, but it is also available for the + kernel's use for its own data structures. Among many + other things, it is where everything from the Slab is + allocated. Bad things happen when you're out of lowmem. + SwapTotal: total amount of swap space available + SwapFree: Memory which has been evicted from RAM, and is temporarily + on the disk + Dirty: Memory which is waiting to get written back to the disk + Writeback: Memory which is actively being written back to the disk + AnonPages: Non-file backed pages mapped into userspace page tables + Mapped: files which have been mmaped, such as libraries + Slab: in-kernel data structures cache +SReclaimable: Part of Slab, that might be reclaimed, such as caches + SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure + PageTables: amount of memory dedicated to the lowest level of page + tables. +NFS_Unstable: NFS pages sent to the server, but not yet committed to stable + storage + Bounce: Memory used for block device "bounce buffers" +WritebackTmp: Memory used by FUSE for temporary writeback buffers + CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), + this is the total amount of memory currently available to + be allocated on the system. This limit is only adhered to + if strict overcommit accounting is enabled (mode 2 in + 'vm.overcommit_memory'). + The CommitLimit is calculated with the following formula: + CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap + For example, on a system with 1G of physical RAM and 7G + of swap with a `vm.overcommit_ratio` of 30 it would + yield a CommitLimit of 7.3G. + For more details, see the memory overcommit documentation + in vm/overcommit-accounting. +Committed_AS: The amount of memory presently allocated on the system. + The committed memory is a sum of all of the memory which + has been allocated by processes, even if it has not been + "used" by them as of yet. A process which malloc()'s 1G + of memory, but only touches 300M of it will only show up + as using 300M of memory even if it has the address space + allocated for the entire 1G. This 1G is memory which has + been "committed" to by the VM and can be used at any time + by the allocating application. With strict overcommit + enabled on the system (mode 2 in 'vm.overcommit_memory'), + allocations which would exceed the CommitLimit (detailed + above) will not be permitted. This is useful if one needs + to guarantee that processes will not fail due to lack of + memory once that memory has been successfully allocated. +VmallocTotal: total size of vmalloc memory area + VmallocUsed: amount of vmalloc area which is used +VmallocChunk: largest contiguous block of vmalloc area which is free + +.............................................................................. + +vmallocinfo: + +Provides information about vmalloced/vmaped areas. One line per area, +containing the virtual address range of the area, size in bytes, +caller information of the creator, and optional information depending +on the kind of area : + + pages=nr number of pages + phys=addr if a physical address was specified + ioremap I/O mapping (ioremap() and friends) + vmalloc vmalloc() area + vmap vmap()ed pages + user VM_USERMAP area + vpages buffer for pages pointers was vmalloced (huge area) + N<node>=nr (Only on NUMA kernels) + Number of pages allocated on memory node <node> + +> cat /proc/vmallocinfo +0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... + /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 +0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... + /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 +0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... + phys=7fee8000 ioremap +0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... + phys=7fee7000 ioremap +0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 +0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... + /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 +0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... + pages=2 vmalloc N1=2 +0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... + /0x130 [x_tables] pages=4 vmalloc N0=4 +0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... + pages=14 vmalloc N2=14 +0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... + pages=4 vmalloc N1=4 +0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... + pages=2 vmalloc N1=2 +0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... + pages=10 vmalloc N0=10 + +.............................................................................. + +softirqs: + +Provides counts of softirq handlers serviced since boot time, for each cpu. + +> cat /proc/softirqs + CPU0 CPU1 CPU2 CPU3 + HI: 0 0 0 0 + TIMER: 27166 27120 27097 27034 + NET_TX: 0 0 0 17 + NET_RX: 42 0 0 39 + BLOCK: 0 0 107 1121 + TASKLET: 0 0 0 290 + SCHED: 27035 26983 26971 26746 + HRTIMER: 0 0 0 0 + RCU: 1678 1769 2178 2250 + + +1.3 IDE devices in /proc/ide +---------------------------- + +The subdirectory /proc/ide contains information about all IDE devices of which +the kernel is aware. There is one subdirectory for each IDE controller, the +file drivers and a link for each IDE device, pointing to the device directory +in the controller specific subtree. + +The file drivers contains general information about the drivers used for the +IDE devices: + + > cat /proc/ide/drivers + ide-cdrom version 4.53 + ide-disk version 1.08 + +More detailed information can be found in the controller specific +subdirectories. These are named ide0, ide1 and so on. Each of these +directories contains the files shown in table 1-6. + + +Table 1-6: IDE controller info in /proc/ide/ide? +.............................................................................. + File Content + channel IDE channel (0 or 1) + config Configuration (only for PCI/IDE bridge) + mate Mate name + model Type/Chipset of IDE controller +.............................................................................. + +Each device connected to a controller has a separate subdirectory in the +controllers directory. The files listed in table 1-7 are contained in these +directories. + + +Table 1-7: IDE device information +.............................................................................. + File Content + cache The cache + capacity Capacity of the medium (in 512Byte blocks) + driver driver and version + geometry physical and logical geometry + identify device identify block + media media type + model device identifier + settings device setup + smart_thresholds IDE disk management thresholds + smart_values IDE disk management values +.............................................................................. + +The most interesting file is settings. This file contains a nice overview of +the drive parameters: + + # cat /proc/ide/ide0/hda/settings + name value min max mode + ---- ----- --- --- ---- + bios_cyl 526 0 65535 rw + bios_head 255 0 255 rw + bios_sect 63 0 63 rw + breada_readahead 4 0 127 rw + bswap 0 0 1 r + file_readahead 72 0 2097151 rw + io_32bit 0 0 3 rw + keepsettings 0 0 1 rw + max_kb_per_request 122 1 127 rw + multcount 0 0 8 rw + nice1 1 0 1 rw + nowerr 0 0 1 rw + pio_mode write-only 0 255 w + slow 0 0 1 rw + unmaskirq 0 0 1 rw + using_dma 0 0 1 rw + + +1.4 Networking info in /proc/net +-------------------------------- + +The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the +additional values you get for IP version 6 if you configure the kernel to +support this. Table 1-9 lists the files and their meaning. + + +Table 1-8: IPv6 info in /proc/net +.............................................................................. + File Content + udp6 UDP sockets (IPv6) + tcp6 TCP sockets (IPv6) + raw6 Raw device statistics (IPv6) + igmp6 IP multicast addresses, which this host joined (IPv6) + if_inet6 List of IPv6 interface addresses + ipv6_route Kernel routing table for IPv6 + rt6_stats Global IPv6 routing tables statistics + sockstat6 Socket statistics (IPv6) + snmp6 Snmp data (IPv6) +.............................................................................. + + +Table 1-9: Network info in /proc/net +.............................................................................. + File Content + arp Kernel ARP table + dev network devices with statistics + dev_mcast the Layer2 multicast groups a device is listening too + (interface index, label, number of references, number of bound + addresses). + dev_stat network device status + ip_fwchains Firewall chain linkage + ip_fwnames Firewall chain names + ip_masq Directory containing the masquerading tables + ip_masquerade Major masquerading table + netstat Network statistics + raw raw device statistics + route Kernel routing table + rpc Directory containing rpc info + rt_cache Routing cache + snmp SNMP data + sockstat Socket statistics + tcp TCP sockets + tr_rif Token ring RIF routing table + udp UDP sockets + unix UNIX domain sockets + wireless Wireless interface data (Wavelan etc) + igmp IP multicast addresses, which this host joined + psched Global packet scheduler parameters. + netlink List of PF_NETLINK sockets + ip_mr_vifs List of multicast virtual interfaces + ip_mr_cache List of multicast routing cache +.............................................................................. + +You can use this information to see which network devices are available in +your system and how much traffic was routed over those devices: + + > cat /proc/net/dev + Inter-|Receive |[... + face |bytes packets errs drop fifo frame compressed multicast|[... + lo: 908188 5596 0 0 0 0 0 0 [... + ppp0:15475140 20721 410 0 0 410 0 0 [... + eth0: 614530 7085 0 0 0 0 0 1 [... + + ...] Transmit + ...] bytes packets errs drop fifo colls carrier compressed + ...] 908188 5596 0 0 0 0 0 0 + ...] 1375103 17405 0 0 0 0 0 0 + ...] 1703981 5535 0 0 0 3 0 0 + +In addition, each Channel Bond interface has its own directory. For +example, the bond0 device will have a directory called /proc/net/bond0/. +It will contain information that is specific to that bond, such as the +current slaves of the bond, the link status of the slaves, and how +many times the slaves link has failed. + +1.5 SCSI info +------------- + +If you have a SCSI host adapter in your system, you'll find a subdirectory +named after the driver for this adapter in /proc/scsi. You'll also see a list +of all recognized SCSI devices in /proc/scsi: + + >cat /proc/scsi/scsi + Attached devices: + Host: scsi0 Channel: 00 Id: 00 Lun: 00 + Vendor: IBM Model: DGHS09U Rev: 03E0 + Type: Direct-Access ANSI SCSI revision: 03 + Host: scsi0 Channel: 00 Id: 06 Lun: 00 + Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 + Type: CD-ROM ANSI SCSI revision: 02 + + +The directory named after the driver has one file for each adapter found in +the system. These files contain information about the controller, including +the used IRQ and the IO address range. The amount of information shown is +dependent on the adapter you use. The example shows the output for an Adaptec +AHA-2940 SCSI adapter: + + > cat /proc/scsi/aic7xxx/0 + + Adaptec AIC7xxx driver version: 5.1.19/3.2.4 + Compile Options: + TCQ Enabled By Default : Disabled + AIC7XXX_PROC_STATS : Disabled + AIC7XXX_RESET_DELAY : 5 + Adapter Configuration: + SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter + Ultra Wide Controller + PCI MMAPed I/O Base: 0xeb001000 + Adapter SEEPROM Config: SEEPROM found and used. + Adaptec SCSI BIOS: Enabled + IRQ: 10 + SCBs: Active 0, Max Active 2, + Allocated 15, HW 16, Page 255 + Interrupts: 160328 + BIOS Control Word: 0x18b6 + Adapter Control Word: 0x005b + Extended Translation: Enabled + Disconnect Enable Flags: 0xffff + Ultra Enable Flags: 0x0001 + Tag Queue Enable Flags: 0x0000 + Ordered Queue Tag Flags: 0x0000 + Default Tag Queue Depth: 8 + Tagged Queue By Device array for aic7xxx host instance 0: + {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} + Actual queue depth per device for aic7xxx host instance 0: + {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} + Statistics: + (scsi0:0:0:0) + Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 + Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) + Total transfers 160151 (74577 reads and 85574 writes) + (scsi0:0:6:0) + Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 + Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) + Total transfers 0 (0 reads and 0 writes) + + +1.6 Parallel port info in /proc/parport +--------------------------------------- + +The directory /proc/parport contains information about the parallel ports of +your system. It has one subdirectory for each port, named after the port +number (0,1,2,...). + +These directories contain the four files shown in Table 1-10. + + +Table 1-10: Files in /proc/parport +.............................................................................. + File Content + autoprobe Any IEEE-1284 device ID information that has been acquired. + devices list of the device drivers using that port. A + will appear by the + name of the device currently using the port (it might not appear + against any). + hardware Parallel port's base address, IRQ line and DMA channel. + irq IRQ that parport is using for that port. This is in a separate + file to allow you to alter it by writing a new value in (IRQ + number or none). +.............................................................................. + +1.7 TTY info in /proc/tty +------------------------- + +Information about the available and actually used tty's can be found in the +directory /proc/tty.You'll find entries for drivers and line disciplines in +this directory, as shown in Table 1-11. + + +Table 1-11: Files in /proc/tty +.............................................................................. + File Content + drivers list of drivers and their usage + ldiscs registered line disciplines + driver/serial usage statistic and status of single tty lines +.............................................................................. + +To see which tty's are currently in use, you can simply look into the file +/proc/tty/drivers: + + > cat /proc/tty/drivers + pty_slave /dev/pts 136 0-255 pty:slave + pty_master /dev/ptm 128 0-255 pty:master + pty_slave /dev/ttyp 3 0-255 pty:slave + pty_master /dev/pty 2 0-255 pty:master + serial /dev/cua 5 64-67 serial:callout + serial /dev/ttyS 4 64-67 serial + /dev/tty0 /dev/tty0 4 0 system:vtmaster + /dev/ptmx /dev/ptmx 5 2 system + /dev/console /dev/console 5 1 system:console + /dev/tty /dev/tty 5 0 system:/dev/tty + unknown /dev/tty 4 1-63 console + + +1.8 Miscellaneous kernel statistics in /proc/stat +------------------------------------------------- + +Various pieces of information about kernel activity are available in the +/proc/stat file. All of the numbers reported in this file are aggregates +since the system first booted. For a quick look, simply cat the file: + + > cat /proc/stat + cpu 2255 34 2290 22625563 6290 127 456 0 0 + cpu0 1132 34 1441 11311718 3675 127 438 0 0 + cpu1 1123 0 849 11313845 2614 0 18 0 0 + intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] + ctxt 1990473 + btime 1062191376 + processes 2915 + procs_running 1 + procs_blocked 0 + softirq 183433 0 21755 12 39 1137 231 21459 2263 + +The very first "cpu" line aggregates the numbers in all of the other "cpuN" +lines. These numbers identify the amount of time the CPU has spent performing +different kinds of work. Time units are in USER_HZ (typically hundredths of a +second). The meanings of the columns are as follows, from left to right: + +- user: normal processes executing in user mode +- nice: niced processes executing in user mode +- system: processes executing in kernel mode +- idle: twiddling thumbs +- iowait: waiting for I/O to complete +- irq: servicing interrupts +- softirq: servicing softirqs +- steal: involuntary wait +- guest: running a normal guest +- guest_nice: running a niced guest + +The "intr" line gives counts of interrupts serviced since boot time, for each +of the possible system interrupts. The first column is the total of all +interrupts serviced; each subsequent column is the total for that particular +interrupt. + +The "ctxt" line gives the total number of context switches across all CPUs. + +The "btime" line gives the time at which the system booted, in seconds since +the Unix epoch. + +The "processes" line gives the number of processes and threads created, which +includes (but is not limited to) those created by calls to the fork() and +clone() system calls. + +The "procs_running" line gives the total number of threads that are +running or ready to run (i.e., the total number of runnable threads). + +The "procs_blocked" line gives the number of processes currently blocked, +waiting for I/O to complete. + +The "softirq" line gives counts of softirqs serviced since boot time, for each +of the possible system softirqs. The first column is the total of all +softirqs serviced; each subsequent column is the total for that particular +softirq. + + +1.9 Ext4 file system parameters +------------------------------ + +Information about mounted ext4 file systems can be found in +/proc/fs/ext4. Each mounted filesystem will have a directory in +/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or +/proc/fs/ext4/dm-0). The files in each per-device directory are shown +in Table 1-12, below. + +Table 1-12: Files in /proc/fs/ext4/<devname> +.............................................................................. + File Content + mb_groups details of multiblock allocator buddy cache of free blocks +.............................................................................. + +2.0 /proc/consoles +------------------ +Shows registered system console lines. + +To see which character device lines are currently used for the system console +/dev/console, you may simply look into the file /proc/consoles: + + > cat /proc/consoles + tty0 -WU (ECp) 4:7 + ttyS0 -W- (Ep) 4:64 + +The columns are: + + device name of the device + operations R = can do read operations + W = can do write operations + U = can do unblank + flags E = it is enabled + C = it is preferred console + B = it is primary boot console + p = it is used for printk buffer + b = it is not a TTY but a Braille device + a = it is safe to use when cpu is offline + major:minor major and minor number of the device separated by a colon + +------------------------------------------------------------------------------ +Summary +------------------------------------------------------------------------------ +The /proc file system serves information about the running system. It not only +allows access to process data but also allows you to request the kernel status +by reading files in the hierarchy. + +The directory structure of /proc reflects the types of information and makes +it easy, if not obvious, where to look for specific data. +------------------------------------------------------------------------------ + +------------------------------------------------------------------------------ +CHAPTER 2: MODIFYING SYSTEM PARAMETERS +------------------------------------------------------------------------------ + +------------------------------------------------------------------------------ +In This Chapter +------------------------------------------------------------------------------ +* Modifying kernel parameters by writing into files found in /proc/sys +* Exploring the files which modify certain parameters +* Review of the /proc/sys file tree +------------------------------------------------------------------------------ + + +A very interesting part of /proc is the directory /proc/sys. This is not only +a source of information, it also allows you to change parameters within the +kernel. Be very careful when attempting this. You can optimize your system, +but you can also cause it to crash. Never alter kernel parameters on a +production system. Set up a development machine and test to make sure that +everything works the way you want it to. You may have no alternative but to +reboot the machine once an error has been made. + +To change a value, simply echo the new value into the file. An example is +given below in the section on the file system data. You need to be root to do +this. You can create your own boot script to perform this every time your +system boots. + +The files in /proc/sys can be used to fine tune and monitor miscellaneous and +general things in the operation of the Linux kernel. Since some of the files +can inadvertently disrupt your system, it is advisable to read both +documentation and source before actually making adjustments. In any case, be +very careful when writing to any of these files. The entries in /proc may +change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt +review the kernel documentation in the directory /usr/src/linux/Documentation. +This chapter is heavily based on the documentation included in the pre 2.2 +kernels, and became part of it in version 2.2.1 of the Linux kernel. + +Please see: Documentation/sysctls/ directory for descriptions of these +entries. + +------------------------------------------------------------------------------ +Summary +------------------------------------------------------------------------------ +Certain aspects of kernel behavior can be modified at runtime, without the +need to recompile the kernel, or even to reboot the system. The files in the +/proc/sys tree can not only be read, but also modified. You can use the echo +command to write value into these files, thereby changing the default settings +of the kernel. +------------------------------------------------------------------------------ + +------------------------------------------------------------------------------ +CHAPTER 3: PER-PROCESS PARAMETERS +------------------------------------------------------------------------------ + +3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score +-------------------------------------------------------------------------------- + +These file can be used to adjust the badness heuristic used to select which +process gets killed in out of memory conditions. + +The badness heuristic assigns a value to each candidate task ranging from 0 +(never kill) to 1000 (always kill) to determine which process is targeted. The +units are roughly a proportion along that range of allowed memory the process +may allocate from based on an estimation of its current memory and swap use. +For example, if a task is using all allowed memory, its badness score will be +1000. If it is using half of its allowed memory, its score will be 500. + +There is an additional factor included in the badness score: root +processes are given 3% extra memory over other tasks. + +The amount of "allowed" memory depends on the context in which the oom killer +was called. If it is due to the memory assigned to the allocating task's cpuset +being exhausted, the allowed memory represents the set of mems assigned to that +cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed +memory represents the set of mempolicy nodes. If it is due to a memory +limit (or swap limit) being reached, the allowed memory is that configured +limit. Finally, if it is due to the entire system being out of memory, the +allowed memory represents all allocatable resources. + +The value of /proc/<pid>/oom_score_adj is added to the badness score before it +is used to determine which task to kill. Acceptable values range from -1000 +(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to +polarize the preference for oom killing either by always preferring a certain +task or completely disabling it. The lowest possible value, -1000, is +equivalent to disabling oom killing entirely for that task since it will always +report a badness score of 0. + +Consequently, it is very simple for userspace to define the amount of memory to +consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for +example, is roughly equivalent to allowing the remainder of tasks sharing the +same system, cpuset, mempolicy, or memory controller resources to use at least +50% more memory. A value of -500, on the other hand, would be roughly +equivalent to discounting 50% of the task's allowed memory from being considered +as scoring against the task. + +For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also +be used to tune the badness score. Its acceptable values range from -16 +(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 +(OOM_DISABLE) to disable oom killing entirely for that task. Its value is +scaled linearly with /proc/<pid>/oom_score_adj. + +Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the +other with its scaled value. + +The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last +value set by a CAP_SYS_RESOURCE process. To reduce the value any lower +requires CAP_SYS_RESOURCE. + +NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see +Documentation/feature-removal-schedule.txt. + +Caveat: when a parent task is selected, the oom killer will sacrifice any first +generation children with separate address spaces instead, if possible. This +avoids servers and important system daemons from being killed and loses the +minimal amount of work. + + +3.2 /proc/<pid>/oom_score - Display current oom-killer score +------------------------------------------------------------- + +This file can be used to check the current score used by the oom-killer is for +any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which +process should be killed in an out-of-memory situation. + + +3.3 /proc/<pid>/io - Display the IO accounting fields +------------------------------------------------------- + +This file contains IO statistics for each running process + +Example +------- + +test:/tmp # dd if=/dev/zero of=/tmp/test.dat & +[1] 3828 + +test:/tmp # cat /proc/3828/io +rchar: 323934931 +wchar: 323929600 +syscr: 632687 +syscw: 632675 +read_bytes: 0 +write_bytes: 323932160 +cancelled_write_bytes: 0 + + +Description +----------- + +rchar +----- + +I/O counter: chars read +The number of bytes which this task has caused to be read from storage. This +is simply the sum of bytes which this process passed to read() and pread(). +It includes things like tty IO and it is unaffected by whether or not actual +physical disk IO was required (the read might have been satisfied from +pagecache) + + +wchar +----- + +I/O counter: chars written +The number of bytes which this task has caused, or shall cause to be written +to disk. Similar caveats apply here as with rchar. + + +syscr +----- + +I/O counter: read syscalls +Attempt to count the number of read I/O operations, i.e. syscalls like read() +and pread(). + + +syscw +----- + +I/O counter: write syscalls +Attempt to count the number of write I/O operations, i.e. syscalls like +write() and pwrite(). + + +read_bytes +---------- + +I/O counter: bytes read +Attempt to count the number of bytes which this process really did cause to +be fetched from the storage layer. Done at the submit_bio() level, so it is +accurate for block-backed filesystems. <please add status regarding NFS and +CIFS at a later time> + + +write_bytes +----------- + +I/O counter: bytes written +Attempt to count the number of bytes which this process caused to be sent to +the storage layer. This is done at page-dirtying time. + + +cancelled_write_bytes +--------------------- + +The big inaccuracy here is truncate. If a process writes 1MB to a file and +then deletes the file, it will in fact perform no writeout. But it will have +been accounted as having caused 1MB of write. +In other words: The number of bytes which this process caused to not happen, +by truncating pagecache. A task can cause "negative" IO too. If this task +truncates some dirty pagecache, some IO which another task has been accounted +for (in its write_bytes) will not be happening. We _could_ just subtract that +from the truncating task's write_bytes, but there is information loss in doing +that. + + +Note +---- + +At its current implementation state, this is a bit racy on 32-bit machines: if +process A reads process B's /proc/pid/io while process B is updating one of +those 64-bit counters, process A could see an intermediate result. + + +More information about this can be found within the taskstats documentation in +Documentation/accounting. + +3.4 /proc/<pid>/coredump_filter - Core dump filtering settings +--------------------------------------------------------------- +When a process is dumped, all anonymous memory is written to a core file as +long as the size of the core file isn't limited. But sometimes we don't want +to dump some memory segments, for example, huge shared memory. Conversely, +sometimes we want to save file-backed memory segments into a core file, not +only the individual files. + +/proc/<pid>/coredump_filter allows you to customize which memory segments +will be dumped when the <pid> process is dumped. coredump_filter is a bitmask +of memory types. If a bit of the bitmask is set, memory segments of the +corresponding memory type are dumped, otherwise they are not dumped. + +The following 7 memory types are supported: + - (bit 0) anonymous private memory + - (bit 1) anonymous shared memory + - (bit 2) file-backed private memory + - (bit 3) file-backed shared memory + - (bit 4) ELF header pages in file-backed private memory areas (it is + effective only if the bit 2 is cleared) + - (bit 5) hugetlb private memory + - (bit 6) hugetlb shared memory + + Note that MMIO pages such as frame buffer are never dumped and vDSO pages + are always dumped regardless of the bitmask status. + + Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only + effected by bit 5-6. + +Default value of coredump_filter is 0x23; this means all anonymous memory +segments and hugetlb private memory are dumped. + +If you don't want to dump all shared memory segments attached to pid 1234, +write 0x21 to the process's proc file. + + $ echo 0x21 > /proc/1234/coredump_filter + +When a new process is created, the process inherits the bitmask status from its +parent. It is useful to set up coredump_filter before the program runs. +For example: + + $ echo 0x7 > /proc/self/coredump_filter + $ ./some_program + +3.5 /proc/<pid>/mountinfo - Information about mounts +-------------------------------------------------------- + +This file contains lines of the form: + +36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue +(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) + +(1) mount ID: unique identifier of the mount (may be reused after umount) +(2) parent ID: ID of parent (or of self for the top of the mount tree) +(3) major:minor: value of st_dev for files on filesystem +(4) root: root of the mount within the filesystem +(5) mount point: mount point relative to the process's root +(6) mount options: per mount options +(7) optional fields: zero or more fields of the form "tag[:value]" +(8) separator: marks the end of the optional fields +(9) filesystem type: name of filesystem of the form "type[.subtype]" +(10) mount source: filesystem specific information or "none" +(11) super options: per super block options + +Parsers should ignore all unrecognised optional fields. Currently the +possible optional fields are: + +shared:X mount is shared in peer group X +master:X mount is slave to peer group X +propagate_from:X mount is slave and receives propagation from peer group X (*) +unbindable mount is unbindable + +(*) X is the closest dominant peer group under the process's root. If +X is the immediate master of the mount, or if there's no dominant peer +group under the same root, then only the "master:X" field is present +and not the "propagate_from:X" field. + +For more information on mount propagation see: + + Documentation/filesystems/sharedsubtree.txt + + +3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm +-------------------------------------------------------- +These files provide a method to access a tasks comm value. It also allows for +a task to set its own or one of its thread siblings comm value. The comm value +is limited in size compared to the cmdline value, so writing anything longer +then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated +comm value. |