2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
2.13 /proc/<pid>/oom_score - Display current oom-killer score
2.14 /proc/<pid>/io - Display the IO accounting fields
+ 2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
+ 2.16 /proc/<pid>/mountinfo - Information about mounts
------------------------------------------------------------------------------
Preface
Table 1-1: Process specific entries in /proc
..............................................................................
- File Content
- 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
- smaps Extension based on maps, presenting the rss size for each mapped file
+ 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
+ smaps Extension based on maps, the rss size for each mapped file
..............................................................................
For example, to get the status information of a process, all you have to do is
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. The statm file contains more detailed information about the
-process memory usage. Its seven fields are explained in Table 1-2.
+process memory usage. Its seven fields are explained in Table 1-2. The stat
+file contains details information about the process itself. Its fields are
+explained in Table 1-3.
Table 1-2: Contents of the statm files (as of 2.6.8-rc3)
dt number of dirty pages (always 0 on 2.6)
..............................................................................
+
+Table 1-3: Contents of the stat files (as of 2.6.22-rc3)
+..............................................................................
+ 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 (obsolete)
+ blocked bitmap of blocked signals (obsolete)
+ sigign bitmap of ignored signals (obsolete)
+ sigcatch bitmap of catched signals (obsolete)
+ 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
+..............................................................................
+
+
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 1-3. Not all of these will be present in your
+/proc and are listed in Table 1-4. 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 1-3: Kernel info in /proc
+Table 1-4: Kernel info in /proc
..............................................................................
File Content
apm Advanced power management info
mounts Mounted filesystems
net Networking info (see text)
partitions Table of partitions known to the system
- pci Depreciated info of PCI bus (new way -> /proc/bus/pci/,
+ 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)
the IO-APIC automatically retry the transmission, so it should not be a big
problem, but you should read the SMP-FAQ.
-In this context it could be interesting to note the new irq directory in 2.4.
+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 occurance of interrupt of the given type.
+
+The above IRQ vectors are displayed only when relevent. 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 one file; prof_cpu_mask
+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
+ 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
> ls /proc/irq/0/
smp_affinity
-The contents of the prof_cpu_mask file and each smp_affinity file for each IRQ
-is the same by default:
+smp_affinity is a bitmask, in which you can specify which CPUs can handle the
+IRQ, you can set it by doing:
- > cat /proc/irq/0/smp_affinity
- ffffffff
+ > echo 1 > /proc/irq/10/smp_affinity
-It's a bitmask, in which you can specify which CPUs can handle the IRQ, you can
-set it by doing:
+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.
- > echo 1 > /proc/irq/prof_cpu_mask
+The contents of each smp_affinity file is the same by default:
+
+ > cat /proc/irq/0/smp_affinity
+ ffffffff
-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 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.
+
+prof_cpu_mask specifies which CPUs are to be profiled by the system wide
+profiler. Default value is ffffffff (all cpus).
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
SwapFree: 0 kB
Dirty: 968 kB
Writeback: 0 kB
+AnonPages: 861800 kB
Mapped: 280372 kB
-Slab: 684068 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
-PageTables: 24448 kB
VmallocTotal: 112216 kB
VmallocUsed: 428 kB
VmallocChunk: 111088 kB
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
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.
- PageTables: amount of memory dedicated to the lowest level of page
- tables.
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contigious block of vmalloc area which is free
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 1-4.
+directories contains the files shown in table 1-5.
-Table 1-4: IDE controller info in /proc/ide/ide?
+Table 1-5: IDE controller info in /proc/ide/ide?
..............................................................................
File Content
channel IDE channel (0 or 1)
..............................................................................
Each device connected to a controller has a separate subdirectory in the
-controllers directory. The files listed in table 1-5 are contained in these
+controllers directory. The files listed in table 1-6 are contained in these
directories.
-Table 1-5: IDE device information
+Table 1-6: IDE device information
..............................................................................
File Content
cache The cache
since the system first booted. For a quick look, simply cat the file:
> cat /proc/stat
- cpu 2255 34 2290 22625563 6290 127 456
- cpu0 1132 34 1441 11311718 3675 127 438
- cpu1 1123 0 849 11313845 2614 0 18
+ cpu 2255 34 2290 22625563 6290 127 456 0
+ cpu0 1132 34 1441 11311718 3675 127 438 0
+ cpu1 1123 0 849 11313845 2614 0 18 0
intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
ctxt 1990473
btime 1062191376
- iowait: waiting for I/O to complete
- irq: servicing interrupts
- softirq: servicing softirqs
+- steal: involuntary wait
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
The "procs_blocked" line gives the number of processes currently blocked,
waiting for I/O to complete.
+1.9 Ext4 file system parameters
+------------------------------
+Ext4 file system have one directory per partition under /proc/fs/ext4/
+# ls /proc/fs/ext4/hdc/
+group_prealloc max_to_scan mb_groups mb_history min_to_scan order2_req
+stats stream_req
+
+mb_groups:
+This file gives the details of mutiblock allocator buddy cache of free blocks
+
+mb_history:
+Multiblock allocation history.
+
+stats:
+This file indicate whether the multiblock allocator should start collecting
+statistics. The statistics are shown during unmount
+
+group_prealloc:
+The multiblock allocator normalize the block allocation request to
+group_prealloc filesystem blocks if we don't have strip value set.
+The stripe value can be specified at mount time or during mke2fs.
+
+max_to_scan:
+How long multiblock allocator can look for a best extent (in found extents)
+
+min_to_scan:
+How long multiblock allocator must look for a best extent
+
+order2_req:
+Multiblock allocator use 2^N search using buddies only for requests greater
+than or equal to order2_req. The request size is specfied in file system
+blocks. A value of 2 indicate only if the requests are greater than or equal
+to 4 blocks.
+
+stream_req:
+Files smaller than stream_req are served by the stream allocator, whose
+purpose is to pack requests as close each to other as possible to
+produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16
+filesystem block size will use group based preallocation.
------------------------------------------------------------------------------
Summary
Denotes the number of inodes the system has allocated. This number will
grow and shrink dynamically.
+nr_open
+-------
+
+Denotes the maximum number of file-handles a process can
+allocate. Default value is 1024*1024 (1048576) which should be
+enough for most machines. Actual limit depends on RLIMIT_NOFILE
+resource limit.
+
nr_free_inodes
--------------
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
+maps_protect
+------------
+
+Enables/Disables the protection of the per-process proc entries "maps" and
+"smaps". When enabled, the contents of these files are visible only to
+readers that are allowed to ptrace() the given process.
+
2.4 /proc/sys/vm - The virtual memory subsystem
-----------------------------------------------
Data which has been dirty in-memory for longer than this interval will be
written out next time a pdflush daemon wakes up.
+highmem_is_dirtyable
+--------------------
+
+Only present if CONFIG_HIGHMEM is set.
+
+This defaults to 0 (false), meaning that the ratios set above are calculated
+as a percentage of lowmem only. This protects against excessive scanning
+in page reclaim, swapping and general VM distress.
+
+Setting this to 1 can be useful on 32 bit machines where you want to make
+random changes within an MMAPed file that is larger than your available
+lowmem without causing large quantities of random IO. Is is safe if the
+behavior of all programs running on the machine is known and memory will
+not be otherwise stressed.
+
legacy_va_layout
----------------
If non-zero, this sysctl disables the new 32-bit mmap mmap layout - the kernel
will use the legacy (2.4) layout for all processes.
-lower_zone_protection
+lowmem_reserve_ratio
---------------------
For some specialised workloads on highmem machines it is dangerous for
mechanism will also defend that region from allocations which could use
highmem or lowmem).
-The `lower_zone_protection' tunable determines how aggressive the kernel is
-in defending these lower zones. The default value is zero - no
-protection at all.
+The `lowmem_reserve_ratio' tunable determines how aggressive the kernel is
+in defending these lower zones.
If you have a machine which uses highmem or ISA DMA and your
applications are using mlock(), or if you are running with no swap then
-you probably should increase the lower_zone_protection setting.
-
-The units of this tunable are fairly vague. It is approximately equal
-to "megabytes," so setting lower_zone_protection=100 will protect around 100
-megabytes of the lowmem zone from user allocations. It will also make
-those 100 megabytes unavailable for use by applications and by
-pagecache, so there is a cost.
-
-The effects of this tunable may be observed by monitoring
-/proc/meminfo:LowFree. Write a single huge file and observe the point
-at which LowFree ceases to fall.
-
-A reasonable value for lower_zone_protection is 100.
+you probably should change the lowmem_reserve_ratio setting.
+
+The lowmem_reserve_ratio is an array. You can see them by reading this file.
+-
+% cat /proc/sys/vm/lowmem_reserve_ratio
+256 256 32
+-
+Note: # of this elements is one fewer than number of zones. Because the highest
+ zone's value is not necessary for following calculation.
+
+But, these values are not used directly. The kernel calculates # of protection
+pages for each zones from them. These are shown as array of protection pages
+in /proc/zoneinfo like followings. (This is an example of x86-64 box).
+Each zone has an array of protection pages like this.
+
+-
+Node 0, zone DMA
+ pages free 1355
+ min 3
+ low 3
+ high 4
+ :
+ :
+ numa_other 0
+ protection: (0, 2004, 2004, 2004)
+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ pagesets
+ cpu: 0 pcp: 0
+ :
+-
+These protections are added to score to judge whether this zone should be used
+for page allocation or should be reclaimed.
+
+In this example, if normal pages (index=2) are required to this DMA zone and
+pages_high is used for watermark, the kernel judges this zone should not be
+used because pages_free(1355) is smaller than watermark + protection[2]
+(4 + 2004 = 2008). If this protection value is 0, this zone would be used for
+normal page requirement. If requirement is DMA zone(index=0), protection[0]
+(=0) is used.
+
+zone[i]'s protection[j] is calculated by following exprssion.
+
+(i < j):
+ zone[i]->protection[j]
+ = (total sums of present_pages from zone[i+1] to zone[j] on the node)
+ / lowmem_reserve_ratio[i];
+(i = j):
+ (should not be protected. = 0;
+(i > j):
+ (not necessary, but looks 0)
+
+The default values of lowmem_reserve_ratio[i] are
+ 256 (if zone[i] means DMA or DMA32 zone)
+ 32 (others).
+As above expression, they are reciprocal number of ratio.
+256 means 1/256. # of protection pages becomes about "0.39%" of total present
+pages of higher zones on the node.
+
+If you would like to protect more pages, smaller values are effective.
+The minimum value is 1 (1/1 -> 100%).
page-cluster
------------
hugetlb_shm_group contains group id that is allowed to create SysV shared
memory segment using hugetlb page.
+hugepages_treat_as_movable
+--------------------------
+
+This parameter is only useful when kernelcore= is specified at boot time to
+create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
+are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
+value written to hugepages_treat_as_movable allows huge pages to be allocated
+from ZONE_MOVABLE.
+
+Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
+pages pool can easily grow or shrink within. Assuming that applications are
+not running that mlock() a lot of memory, it is likely the huge pages pool
+can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
+into nr_hugepages and triggering page reclaim.
+
laptop_mode
-----------
laptop_mode is a knob that controls "laptop mode". All the things that are
-controlled by this knob are discussed in Documentation/laptop-mode.txt.
+controlled by this knob are discussed in Documentation/laptops/laptop-mode.txt.
block_dump
----------
block_dump enables block I/O debugging when set to a nonzero value. More
-information on block I/O debugging is in Documentation/laptop-mode.txt.
+information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
swap_token_timeout
------------------
Maximum size of the routing cache. Old entries will be purged once the cache
reached has this size.
-max_delay, min_delay
---------------------
-
-Delays for flushing the routing cache.
-
redirect_load, redirect_number
------------------------------
More information about this can be found within the taskstats documentation in
Documentation/accounting.
+2.15 /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 4 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
+
+ Note that MMIO pages such as frame buffer are never dumped and vDSO pages
+ are always dumped regardless of the bitmask status.
+
+Default value of coredump_filter is 0x3; this means all anonymous memory
+segments are dumped.
+
+If you don't want to dump all shared memory segments attached to pid 1234,
+write 1 to the process's proc file.
+
+ $ echo 0x1 > /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
+
+2.16 /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
+
------------------------------------------------------------------------------