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Diffstat (limited to 'Documentation/filesystems/proc.txt')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 169 |
1 files changed, 123 insertions, 46 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 0d07513a67a6..a6aca8740883 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -33,7 +33,8 @@ Table of Contents 2 Modifying System Parameters 3 Per-Process Parameters - 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score + 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 @@ -73,9 +74,9 @@ 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://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version. +http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html -If the above direction does not works for you, ypu could try the kernel +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. @@ -164,6 +165,7 @@ read the file /proc/PID/status: VmExe: 68 kB VmLib: 1412 kB VmPTE: 20 kb + VmSwap: 0 kB Threads: 1 SigQ: 0/28578 SigPnd: 0000000000000000 @@ -188,7 +190,13 @@ 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. -Table 1-2: Contents of the statm files (as of 2.6.30-rc7) +(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 @@ -213,6 +221,7 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7) 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 @@ -297,7 +306,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7) cgtime guest time of the task children in jiffies .............................................................................. -The /proc/PID/map file containing the currently mapped memory regions and +The /proc/PID/maps file containing the currently mapped memory regions and their access permissions. The format is: @@ -308,7 +317,7 @@ address perms offset dev inode pathname 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 [threadstack:001ff4b4] +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 @@ -344,7 +353,6 @@ is not associated with a file: [stack] = the stack of the main process [vdso] = the "virtual dynamic shared object", the kernel system call handler - [threadstack:xxxxxxxx] = the stack of the thread, xxxxxxxx is the stack size or if empty, the mapping is anonymous. @@ -430,6 +438,7 @@ Table 1-5: Kernel info in /proc 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) @@ -557,6 +566,10 @@ 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). @@ -584,7 +597,7 @@ 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 ... -Memory fragmentation is a problem under some workloads, and buddyinfo is a +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. @@ -594,6 +607,48 @@ 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: @@ -914,7 +969,7 @@ your system and how much traffic was routed over those devices: ...] 1375103 17405 0 0 0 0 0 0 ...] 1703981 5535 0 0 0 3 0 0 -In addition, each Channel Bond interface has it's own directory. For +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 @@ -1180,42 +1235,64 @@ of the kernel. CHAPTER 3: PER-PROCESS PARAMETERS ------------------------------------------------------------------------------ -3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score ------------------------------------------------------- - -This file can be used to adjust the score used to select which processes -should be killed in an out-of-memory situation. Giving it a high score will -increase the likelihood of this process being killed by the oom-killer. Valid -values are in the range -16 to +15, plus the special value -17, which disables -oom-killing altogether for this process. - -The process to be killed in an out-of-memory situation is selected among all others -based on its badness score. This value equals the original memory size of the process -and is then updated according to its CPU time (utime + stime) and the -run time (uptime - start time). The longer it runs the smaller is the score. -Badness score is divided by the square root of the CPU time and then by -the double square root of the run time. - -Swapped out tasks are killed first. Half of each child's memory size is added to -the parent's score if they do not share the same memory. Thus forking servers -are the prime candidates to be killed. Having only one 'hungry' child will make -parent less preferable than the child. - -/proc/<pid>/oom_score shows process' current badness score. - -The following heuristics are then applied: - * if the task was reniced, its score doubles - * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE - or CAP_SYS_RAWIO) have their score divided by 4 - * if oom condition happened in one cpuset and checked process does not belong - to it, its score is divided by 8 - * the resulting score is multiplied by two to the power of oom_adj, i.e. - points <<= oom_adj when it is positive and - points >>= -(oom_adj) otherwise - -The task with the highest badness score is then selected and its children -are killed, process itself will be killed in an OOM situation when it does -not have children or some of them disabled oom like described above. +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. + +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 seperate 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 ------------------------------------------------------------- @@ -1311,7 +1388,7 @@ 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 it's write_bytes) will not be happening. We _could_ just subtract that +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. |