mirror of
https://github.com/adulau/aha.git
synced 2024-12-28 11:46:19 +00:00
Update of Documentation: vm.txt and proc.txt
Update Documentation/sysctl/vm.txt and Documentation/filesystems/proc.txt. More specifically, the section on /proc/sys/vm in Documentation/filesystems/proc.txt was removed and a link to Documentation/sysctl/vm.txt added. Most of the verbiage from proc.txt was simply moved in vm.txt, with new addtional text for "swappiness" and "stat_interval". Signed-off-by: Peter W Morreale <pmorreale@novell.com> Acked-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter W Morreale
Linus Torvalds
parent
b5db0e3865
commit
db0fb1848a
2 changed files with 451 additions and 484 deletions
|
|
@ -1371,292 +1371,8 @@ auto_msgmni default value is 1.
|
||||||
2.4 /proc/sys/vm - The virtual memory subsystem
|
2.4 /proc/sys/vm - The virtual memory subsystem
|
||||||
-----------------------------------------------
|
-----------------------------------------------
|
||||||
|
|
||||||
The files in this directory can be used to tune the operation of the virtual
|
Please see: Documentation/sysctls/vm.txt for a description of these
|
||||||
memory (VM) subsystem of the Linux kernel.
|
entries.
|
||||||
|
|
||||||
vfs_cache_pressure
|
|
||||||
------------------
|
|
||||||
|
|
||||||
Controls the tendency of the kernel to reclaim the memory which is used for
|
|
||||||
caching of directory and inode objects.
|
|
||||||
|
|
||||||
At the default value of vfs_cache_pressure=100 the kernel will attempt to
|
|
||||||
reclaim dentries and inodes at a "fair" rate with respect to pagecache and
|
|
||||||
swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer
|
|
||||||
to retain dentry and inode caches. Increasing vfs_cache_pressure beyond 100
|
|
||||||
causes the kernel to prefer to reclaim dentries and inodes.
|
|
||||||
|
|
||||||
dirty_background_bytes
|
|
||||||
----------------------
|
|
||||||
|
|
||||||
Contains the amount of dirty memory at which the pdflush background writeback
|
|
||||||
daemon will start writeback.
|
|
||||||
|
|
||||||
If dirty_background_bytes is written, dirty_background_ratio becomes a function
|
|
||||||
of its value (dirty_background_bytes / the amount of dirtyable system memory).
|
|
||||||
|
|
||||||
dirty_background_ratio
|
|
||||||
----------------------
|
|
||||||
|
|
||||||
Contains, as a percentage of the dirtyable system memory (free pages + mapped
|
|
||||||
pages + file cache, not including locked pages and HugePages), the number of
|
|
||||||
pages at which the pdflush background writeback daemon will start writing out
|
|
||||||
dirty data.
|
|
||||||
|
|
||||||
If dirty_background_ratio is written, dirty_background_bytes becomes a function
|
|
||||||
of its value (dirty_background_ratio * the amount of dirtyable system memory).
|
|
||||||
|
|
||||||
dirty_bytes
|
|
||||||
-----------
|
|
||||||
|
|
||||||
Contains the amount of dirty memory at which a process generating disk writes
|
|
||||||
will itself start writeback.
|
|
||||||
|
|
||||||
If dirty_bytes is written, dirty_ratio becomes a function of its value
|
|
||||||
(dirty_bytes / the amount of dirtyable system memory).
|
|
||||||
|
|
||||||
dirty_ratio
|
|
||||||
-----------
|
|
||||||
|
|
||||||
Contains, as a percentage of the dirtyable system memory (free pages + mapped
|
|
||||||
pages + file cache, not including locked pages and HugePages), the number of
|
|
||||||
pages at which a process which is generating disk writes will itself start
|
|
||||||
writing out dirty data.
|
|
||||||
|
|
||||||
If dirty_ratio is written, dirty_bytes becomes a function of its value
|
|
||||||
(dirty_ratio * the amount of dirtyable system memory).
|
|
||||||
|
|
||||||
dirty_writeback_centisecs
|
|
||||||
-------------------------
|
|
||||||
|
|
||||||
The pdflush writeback daemons will periodically wake up and write `old' data
|
|
||||||
out to disk. This tunable expresses the interval between those wakeups, in
|
|
||||||
100'ths of a second.
|
|
||||||
|
|
||||||
Setting this to zero disables periodic writeback altogether.
|
|
||||||
|
|
||||||
dirty_expire_centisecs
|
|
||||||
----------------------
|
|
||||||
|
|
||||||
This tunable is used to define when dirty data is old enough to be eligible
|
|
||||||
for writeout by the pdflush daemons. It is expressed in 100'ths of a second.
|
|
||||||
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.
|
|
||||||
|
|
||||||
lowmem_reserve_ratio
|
|
||||||
---------------------
|
|
||||||
|
|
||||||
For some specialised workloads on highmem machines it is dangerous for
|
|
||||||
the kernel to allow process memory to be allocated from the "lowmem"
|
|
||||||
zone. This is because that memory could then be pinned via the mlock()
|
|
||||||
system call, or by unavailability of swapspace.
|
|
||||||
|
|
||||||
And on large highmem machines this lack of reclaimable lowmem memory
|
|
||||||
can be fatal.
|
|
||||||
|
|
||||||
So the Linux page allocator has a mechanism which prevents allocations
|
|
||||||
which _could_ use highmem from using too much lowmem. This means that
|
|
||||||
a certain amount of lowmem is defended from the possibility of being
|
|
||||||
captured into pinned user memory.
|
|
||||||
|
|
||||||
(The same argument applies to the old 16 megabyte ISA DMA region. This
|
|
||||||
mechanism will also defend that region from allocations which could use
|
|
||||||
highmem or lowmem).
|
|
||||||
|
|
||||||
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 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 expression.
|
|
||||||
|
|
||||||
(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
|
|
||||||
------------
|
|
||||||
|
|
||||||
page-cluster controls the number of pages which are written to swap in
|
|
||||||
a single attempt. The swap I/O size.
|
|
||||||
|
|
||||||
It is a logarithmic value - setting it to zero means "1 page", setting
|
|
||||||
it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
|
|
||||||
|
|
||||||
The default value is three (eight pages at a time). There may be some
|
|
||||||
small benefits in tuning this to a different value if your workload is
|
|
||||||
swap-intensive.
|
|
||||||
|
|
||||||
overcommit_memory
|
|
||||||
-----------------
|
|
||||||
|
|
||||||
Controls overcommit of system memory, possibly allowing processes
|
|
||||||
to allocate (but not use) more memory than is actually available.
|
|
||||||
|
|
||||||
|
|
||||||
0 - Heuristic overcommit handling. Obvious overcommits of
|
|
||||||
address space are refused. Used for a typical system. It
|
|
||||||
ensures a seriously wild allocation fails while allowing
|
|
||||||
overcommit to reduce swap usage. root is allowed to
|
|
||||||
allocate slightly more memory in this mode. This is the
|
|
||||||
default.
|
|
||||||
|
|
||||||
1 - Always overcommit. Appropriate for some scientific
|
|
||||||
applications.
|
|
||||||
|
|
||||||
2 - Don't overcommit. The total address space commit
|
|
||||||
for the system is not permitted to exceed swap plus a
|
|
||||||
configurable percentage (default is 50) of physical RAM.
|
|
||||||
Depending on the percentage you use, in most situations
|
|
||||||
this means a process will not be killed while attempting
|
|
||||||
to use already-allocated memory but will receive errors
|
|
||||||
on memory allocation as appropriate.
|
|
||||||
|
|
||||||
overcommit_ratio
|
|
||||||
----------------
|
|
||||||
|
|
||||||
Percentage of physical memory size to include in overcommit calculations
|
|
||||||
(see above.)
|
|
||||||
|
|
||||||
Memory allocation limit = swapspace + physmem * (overcommit_ratio / 100)
|
|
||||||
|
|
||||||
swapspace = total size of all swap areas
|
|
||||||
physmem = size of physical memory in system
|
|
||||||
|
|
||||||
nr_hugepages and hugetlb_shm_group
|
|
||||||
----------------------------------
|
|
||||||
|
|
||||||
nr_hugepages configures number of hugetlb page reserved for the system.
|
|
||||||
|
|
||||||
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/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/laptops/laptop-mode.txt.
|
|
||||||
|
|
||||||
swap_token_timeout
|
|
||||||
------------------
|
|
||||||
|
|
||||||
This file contains valid hold time of swap out protection token. The Linux
|
|
||||||
VM has token based thrashing control mechanism and uses the token to prevent
|
|
||||||
unnecessary page faults in thrashing situation. The unit of the value is
|
|
||||||
second. The value would be useful to tune thrashing behavior.
|
|
||||||
|
|
||||||
drop_caches
|
|
||||||
-----------
|
|
||||||
|
|
||||||
Writing to this will cause the kernel to drop clean caches, dentries and
|
|
||||||
inodes from memory, causing that memory to become free.
|
|
||||||
|
|
||||||
To free pagecache:
|
|
||||||
echo 1 > /proc/sys/vm/drop_caches
|
|
||||||
To free dentries and inodes:
|
|
||||||
echo 2 > /proc/sys/vm/drop_caches
|
|
||||||
To free pagecache, dentries and inodes:
|
|
||||||
echo 3 > /proc/sys/vm/drop_caches
|
|
||||||
|
|
||||||
As this is a non-destructive operation and dirty objects are not freeable, the
|
|
||||||
user should run `sync' first.
|
|
||||||
|
|
||||||
|
|
||||||
2.5 /proc/sys/dev - Device specific parameters
|
2.5 /proc/sys/dev - Device specific parameters
|
||||||
|
|
|
||||||
|
|
@ -1,12 +1,13 @@
|
||||||
Documentation for /proc/sys/vm/* kernel version 2.2.10
|
Documentation for /proc/sys/vm/* kernel version 2.6.29
|
||||||
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
|
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
|
||||||
|
(c) 2008 Peter W. Morreale <pmorreale@novell.com>
|
||||||
|
|
||||||
For general info and legal blurb, please look in README.
|
For general info and legal blurb, please look in README.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
This file contains the documentation for the sysctl files in
|
This file contains the documentation for the sysctl files in
|
||||||
/proc/sys/vm and is valid for Linux kernel version 2.2.
|
/proc/sys/vm and is valid for Linux kernel version 2.6.29.
|
||||||
|
|
||||||
The files in this directory can be used to tune the operation
|
The files in this directory can be used to tune the operation
|
||||||
of the virtual memory (VM) subsystem of the Linux kernel and
|
of the virtual memory (VM) subsystem of the Linux kernel and
|
||||||
|
|
@ -16,83 +17,244 @@ Default values and initialization routines for most of these
|
||||||
files can be found in mm/swap.c.
|
files can be found in mm/swap.c.
|
||||||
|
|
||||||
Currently, these files are in /proc/sys/vm:
|
Currently, these files are in /proc/sys/vm:
|
||||||
- overcommit_memory
|
|
||||||
- page-cluster
|
- block_dump
|
||||||
- dirty_ratio
|
- dirty_background_bytes
|
||||||
- dirty_background_ratio
|
- dirty_background_ratio
|
||||||
|
- dirty_bytes
|
||||||
- dirty_expire_centisecs
|
- dirty_expire_centisecs
|
||||||
|
- dirty_ratio
|
||||||
- dirty_writeback_centisecs
|
- dirty_writeback_centisecs
|
||||||
- highmem_is_dirtyable (only if CONFIG_HIGHMEM set)
|
- drop_caches
|
||||||
|
- hugepages_treat_as_movable
|
||||||
|
- hugetlb_shm_group
|
||||||
|
- laptop_mode
|
||||||
|
- legacy_va_layout
|
||||||
|
- lowmem_reserve_ratio
|
||||||
- max_map_count
|
- max_map_count
|
||||||
- min_free_kbytes
|
- min_free_kbytes
|
||||||
- laptop_mode
|
|
||||||
- block_dump
|
|
||||||
- drop-caches
|
|
||||||
- zone_reclaim_mode
|
|
||||||
- min_unmapped_ratio
|
|
||||||
- min_slab_ratio
|
- min_slab_ratio
|
||||||
- panic_on_oom
|
- min_unmapped_ratio
|
||||||
- oom_dump_tasks
|
- mmap_min_addr
|
||||||
- oom_kill_allocating_task
|
|
||||||
- mmap_min_address
|
|
||||||
- numa_zonelist_order
|
|
||||||
- nr_hugepages
|
- nr_hugepages
|
||||||
- nr_overcommit_hugepages
|
- nr_overcommit_hugepages
|
||||||
- nr_trim_pages (only if CONFIG_MMU=n)
|
- nr_pdflush_threads
|
||||||
|
- nr_trim_pages (only if CONFIG_MMU=n)
|
||||||
|
- numa_zonelist_order
|
||||||
|
- oom_dump_tasks
|
||||||
|
- oom_kill_allocating_task
|
||||||
|
- overcommit_memory
|
||||||
|
- overcommit_ratio
|
||||||
|
- page-cluster
|
||||||
|
- panic_on_oom
|
||||||
|
- percpu_pagelist_fraction
|
||||||
|
- stat_interval
|
||||||
|
- swappiness
|
||||||
|
- vfs_cache_pressure
|
||||||
|
- zone_reclaim_mode
|
||||||
|
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
dirty_bytes, dirty_ratio, dirty_background_bytes,
|
block_dump
|
||||||
dirty_background_ratio, dirty_expire_centisecs,
|
|
||||||
dirty_writeback_centisecs, highmem_is_dirtyable,
|
|
||||||
vfs_cache_pressure, laptop_mode, block_dump, swap_token_timeout,
|
|
||||||
drop-caches, hugepages_treat_as_movable:
|
|
||||||
|
|
||||||
See Documentation/filesystems/proc.txt
|
block_dump enables block I/O debugging when set to a nonzero value. More
|
||||||
|
information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
overcommit_memory:
|
dirty_background_bytes
|
||||||
|
|
||||||
This value contains a flag that enables memory overcommitment.
|
Contains the amount of dirty memory at which the pdflush background writeback
|
||||||
|
daemon will start writeback.
|
||||||
|
|
||||||
When this flag is 0, the kernel attempts to estimate the amount
|
If dirty_background_bytes is written, dirty_background_ratio becomes a function
|
||||||
of free memory left when userspace requests more memory.
|
of its value (dirty_background_bytes / the amount of dirtyable system memory).
|
||||||
|
|
||||||
When this flag is 1, the kernel pretends there is always enough
|
|
||||||
memory until it actually runs out.
|
|
||||||
|
|
||||||
When this flag is 2, the kernel uses a "never overcommit"
|
|
||||||
policy that attempts to prevent any overcommit of memory.
|
|
||||||
|
|
||||||
This feature can be very useful because there are a lot of
|
|
||||||
programs that malloc() huge amounts of memory "just-in-case"
|
|
||||||
and don't use much of it.
|
|
||||||
|
|
||||||
The default value is 0.
|
|
||||||
|
|
||||||
See Documentation/vm/overcommit-accounting and
|
|
||||||
security/commoncap.c::cap_vm_enough_memory() for more information.
|
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
overcommit_ratio:
|
dirty_background_ratio
|
||||||
|
|
||||||
When overcommit_memory is set to 2, the committed address
|
Contains, as a percentage of total system memory, the number of pages at which
|
||||||
space is not permitted to exceed swap plus this percentage
|
the pdflush background writeback daemon will start writing out dirty data.
|
||||||
of physical RAM. See above.
|
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
page-cluster:
|
dirty_bytes
|
||||||
|
|
||||||
The Linux VM subsystem avoids excessive disk seeks by reading
|
Contains the amount of dirty memory at which a process generating disk writes
|
||||||
multiple pages on a page fault. The number of pages it reads
|
will itself start writeback.
|
||||||
is dependent on the amount of memory in your machine.
|
|
||||||
|
|
||||||
The number of pages the kernel reads in at once is equal to
|
If dirty_bytes is written, dirty_ratio becomes a function of its value
|
||||||
2 ^ page-cluster. Values above 2 ^ 5 don't make much sense
|
(dirty_bytes / the amount of dirtyable system memory).
|
||||||
for swap because we only cluster swap data in 32-page groups.
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
dirty_expire_centisecs
|
||||||
|
|
||||||
|
This tunable is used to define when dirty data is old enough to be eligible
|
||||||
|
for writeout by the pdflush daemons. It is expressed in 100'ths of a second.
|
||||||
|
Data which has been dirty in-memory for longer than this interval will be
|
||||||
|
written out next time a pdflush daemon wakes up.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
dirty_ratio
|
||||||
|
|
||||||
|
Contains, as a percentage of total system memory, the number of pages at which
|
||||||
|
a process which is generating disk writes will itself start writing out dirty
|
||||||
|
data.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
dirty_writeback_centisecs
|
||||||
|
|
||||||
|
The pdflush writeback daemons will periodically wake up and write `old' data
|
||||||
|
out to disk. This tunable expresses the interval between those wakeups, in
|
||||||
|
100'ths of a second.
|
||||||
|
|
||||||
|
Setting this to zero disables periodic writeback altogether.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
drop_caches
|
||||||
|
|
||||||
|
Writing to this will cause the kernel to drop clean caches, dentries and
|
||||||
|
inodes from memory, causing that memory to become free.
|
||||||
|
|
||||||
|
To free pagecache:
|
||||||
|
echo 1 > /proc/sys/vm/drop_caches
|
||||||
|
To free dentries and inodes:
|
||||||
|
echo 2 > /proc/sys/vm/drop_caches
|
||||||
|
To free pagecache, dentries and inodes:
|
||||||
|
echo 3 > /proc/sys/vm/drop_caches
|
||||||
|
|
||||||
|
As this is a non-destructive operation and dirty objects are not freeable, the
|
||||||
|
user should run `sync' first.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
hugetlb_shm_group
|
||||||
|
|
||||||
|
hugetlb_shm_group contains group id that is allowed to create SysV
|
||||||
|
shared memory segment using hugetlb page.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
laptop_mode
|
||||||
|
|
||||||
|
laptop_mode is a knob that controls "laptop mode". All the things that are
|
||||||
|
controlled by this knob are discussed in Documentation/laptops/laptop-mode.txt.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
lowmem_reserve_ratio
|
||||||
|
|
||||||
|
For some specialised workloads on highmem machines it is dangerous for
|
||||||
|
the kernel to allow process memory to be allocated from the "lowmem"
|
||||||
|
zone. This is because that memory could then be pinned via the mlock()
|
||||||
|
system call, or by unavailability of swapspace.
|
||||||
|
|
||||||
|
And on large highmem machines this lack of reclaimable lowmem memory
|
||||||
|
can be fatal.
|
||||||
|
|
||||||
|
So the Linux page allocator has a mechanism which prevents allocations
|
||||||
|
which _could_ use highmem from using too much lowmem. This means that
|
||||||
|
a certain amount of lowmem is defended from the possibility of being
|
||||||
|
captured into pinned user memory.
|
||||||
|
|
||||||
|
(The same argument applies to the old 16 megabyte ISA DMA region. This
|
||||||
|
mechanism will also defend that region from allocations which could use
|
||||||
|
highmem or lowmem).
|
||||||
|
|
||||||
|
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 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 expression.
|
||||||
|
|
||||||
|
(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%).
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
|
|
@ -113,9 +275,9 @@ The default value is 65536.
|
||||||
|
|
||||||
min_free_kbytes:
|
min_free_kbytes:
|
||||||
|
|
||||||
This is used to force the Linux VM to keep a minimum number
|
This is used to force the Linux VM to keep a minimum number
|
||||||
of kilobytes free. The VM uses this number to compute a pages_min
|
of kilobytes free. The VM uses this number to compute a pages_min
|
||||||
value for each lowmem zone in the system. Each lowmem zone gets
|
value for each lowmem zone in the system. Each lowmem zone gets
|
||||||
a number of reserved free pages based proportionally on its size.
|
a number of reserved free pages based proportionally on its size.
|
||||||
|
|
||||||
Some minimal amount of memory is needed to satisfy PF_MEMALLOC
|
Some minimal amount of memory is needed to satisfy PF_MEMALLOC
|
||||||
|
|
@ -124,73 +286,6 @@ become subtly broken, and prone to deadlock under high loads.
|
||||||
|
|
||||||
Setting this too high will OOM your machine instantly.
|
Setting this too high will OOM your machine instantly.
|
||||||
|
|
||||||
==============================================================
|
|
||||||
|
|
||||||
percpu_pagelist_fraction
|
|
||||||
|
|
||||||
This is the fraction of pages at most (high mark pcp->high) in each zone that
|
|
||||||
are allocated for each per cpu page list. The min value for this is 8. It
|
|
||||||
means that we don't allow more than 1/8th of pages in each zone to be
|
|
||||||
allocated in any single per_cpu_pagelist. This entry only changes the value
|
|
||||||
of hot per cpu pagelists. User can specify a number like 100 to allocate
|
|
||||||
1/100th of each zone to each per cpu page list.
|
|
||||||
|
|
||||||
The batch value of each per cpu pagelist is also updated as a result. It is
|
|
||||||
set to pcp->high/4. The upper limit of batch is (PAGE_SHIFT * 8)
|
|
||||||
|
|
||||||
The initial value is zero. Kernel does not use this value at boot time to set
|
|
||||||
the high water marks for each per cpu page list.
|
|
||||||
|
|
||||||
===============================================================
|
|
||||||
|
|
||||||
zone_reclaim_mode:
|
|
||||||
|
|
||||||
Zone_reclaim_mode allows someone to set more or less aggressive approaches to
|
|
||||||
reclaim memory when a zone runs out of memory. If it is set to zero then no
|
|
||||||
zone reclaim occurs. Allocations will be satisfied from other zones / nodes
|
|
||||||
in the system.
|
|
||||||
|
|
||||||
This is value ORed together of
|
|
||||||
|
|
||||||
1 = Zone reclaim on
|
|
||||||
2 = Zone reclaim writes dirty pages out
|
|
||||||
4 = Zone reclaim swaps pages
|
|
||||||
|
|
||||||
zone_reclaim_mode is set during bootup to 1 if it is determined that pages
|
|
||||||
from remote zones will cause a measurable performance reduction. The
|
|
||||||
page allocator will then reclaim easily reusable pages (those page
|
|
||||||
cache pages that are currently not used) before allocating off node pages.
|
|
||||||
|
|
||||||
It may be beneficial to switch off zone reclaim if the system is
|
|
||||||
used for a file server and all of memory should be used for caching files
|
|
||||||
from disk. In that case the caching effect is more important than
|
|
||||||
data locality.
|
|
||||||
|
|
||||||
Allowing zone reclaim to write out pages stops processes that are
|
|
||||||
writing large amounts of data from dirtying pages on other nodes. Zone
|
|
||||||
reclaim will write out dirty pages if a zone fills up and so effectively
|
|
||||||
throttle the process. This may decrease the performance of a single process
|
|
||||||
since it cannot use all of system memory to buffer the outgoing writes
|
|
||||||
anymore but it preserve the memory on other nodes so that the performance
|
|
||||||
of other processes running on other nodes will not be affected.
|
|
||||||
|
|
||||||
Allowing regular swap effectively restricts allocations to the local
|
|
||||||
node unless explicitly overridden by memory policies or cpuset
|
|
||||||
configurations.
|
|
||||||
|
|
||||||
=============================================================
|
|
||||||
|
|
||||||
min_unmapped_ratio:
|
|
||||||
|
|
||||||
This is available only on NUMA kernels.
|
|
||||||
|
|
||||||
A percentage of the total pages in each zone. Zone reclaim will only
|
|
||||||
occur if more than this percentage of pages are file backed and unmapped.
|
|
||||||
This is to insure that a minimal amount of local pages is still available for
|
|
||||||
file I/O even if the node is overallocated.
|
|
||||||
|
|
||||||
The default is 1 percent.
|
|
||||||
|
|
||||||
=============================================================
|
=============================================================
|
||||||
|
|
||||||
min_slab_ratio:
|
min_slab_ratio:
|
||||||
|
|
@ -211,69 +306,16 @@ and may not be fast.
|
||||||
|
|
||||||
=============================================================
|
=============================================================
|
||||||
|
|
||||||
panic_on_oom
|
min_unmapped_ratio:
|
||||||
|
|
||||||
This enables or disables panic on out-of-memory feature.
|
This is available only on NUMA kernels.
|
||||||
|
|
||||||
If this is set to 0, the kernel will kill some rogue process,
|
A percentage of the total pages in each zone. Zone reclaim will only
|
||||||
called oom_killer. Usually, oom_killer can kill rogue processes and
|
occur if more than this percentage of pages are file backed and unmapped.
|
||||||
system will survive.
|
This is to insure that a minimal amount of local pages is still available for
|
||||||
|
file I/O even if the node is overallocated.
|
||||||
|
|
||||||
If this is set to 1, the kernel panics when out-of-memory happens.
|
The default is 1 percent.
|
||||||
However, if a process limits using nodes by mempolicy/cpusets,
|
|
||||||
and those nodes become memory exhaustion status, one process
|
|
||||||
may be killed by oom-killer. No panic occurs in this case.
|
|
||||||
Because other nodes' memory may be free. This means system total status
|
|
||||||
may be not fatal yet.
|
|
||||||
|
|
||||||
If this is set to 2, the kernel panics compulsorily even on the
|
|
||||||
above-mentioned.
|
|
||||||
|
|
||||||
The default value is 0.
|
|
||||||
1 and 2 are for failover of clustering. Please select either
|
|
||||||
according to your policy of failover.
|
|
||||||
|
|
||||||
=============================================================
|
|
||||||
|
|
||||||
oom_dump_tasks
|
|
||||||
|
|
||||||
Enables a system-wide task dump (excluding kernel threads) to be
|
|
||||||
produced when the kernel performs an OOM-killing and includes such
|
|
||||||
information as pid, uid, tgid, vm size, rss, cpu, oom_adj score, and
|
|
||||||
name. This is helpful to determine why the OOM killer was invoked
|
|
||||||
and to identify the rogue task that caused it.
|
|
||||||
|
|
||||||
If this is set to zero, this information is suppressed. On very
|
|
||||||
large systems with thousands of tasks it may not be feasible to dump
|
|
||||||
the memory state information for each one. Such systems should not
|
|
||||||
be forced to incur a performance penalty in OOM conditions when the
|
|
||||||
information may not be desired.
|
|
||||||
|
|
||||||
If this is set to non-zero, this information is shown whenever the
|
|
||||||
OOM killer actually kills a memory-hogging task.
|
|
||||||
|
|
||||||
The default value is 0.
|
|
||||||
|
|
||||||
=============================================================
|
|
||||||
|
|
||||||
oom_kill_allocating_task
|
|
||||||
|
|
||||||
This enables or disables killing the OOM-triggering task in
|
|
||||||
out-of-memory situations.
|
|
||||||
|
|
||||||
If this is set to zero, the OOM killer will scan through the entire
|
|
||||||
tasklist and select a task based on heuristics to kill. This normally
|
|
||||||
selects a rogue memory-hogging task that frees up a large amount of
|
|
||||||
memory when killed.
|
|
||||||
|
|
||||||
If this is set to non-zero, the OOM killer simply kills the task that
|
|
||||||
triggered the out-of-memory condition. This avoids the expensive
|
|
||||||
tasklist scan.
|
|
||||||
|
|
||||||
If panic_on_oom is selected, it takes precedence over whatever value
|
|
||||||
is used in oom_kill_allocating_task.
|
|
||||||
|
|
||||||
The default value is 0.
|
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
|
|
@ -290,6 +332,50 @@ against future potential kernel bugs.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
|
nr_hugepages
|
||||||
|
|
||||||
|
Change the minimum size of the hugepage pool.
|
||||||
|
|
||||||
|
See Documentation/vm/hugetlbpage.txt
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
nr_overcommit_hugepages
|
||||||
|
|
||||||
|
Change the maximum size of the hugepage pool. The maximum is
|
||||||
|
nr_hugepages + nr_overcommit_hugepages.
|
||||||
|
|
||||||
|
See Documentation/vm/hugetlbpage.txt
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
nr_pdflush_threads
|
||||||
|
|
||||||
|
The current number of pdflush threads. This value is read-only.
|
||||||
|
The value changes according to the number of dirty pages in the system.
|
||||||
|
|
||||||
|
When neccessary, additional pdflush threads are created, one per second, up to
|
||||||
|
nr_pdflush_threads_max.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
nr_trim_pages
|
||||||
|
|
||||||
|
This is available only on NOMMU kernels.
|
||||||
|
|
||||||
|
This value adjusts the excess page trimming behaviour of power-of-2 aligned
|
||||||
|
NOMMU mmap allocations.
|
||||||
|
|
||||||
|
A value of 0 disables trimming of allocations entirely, while a value of 1
|
||||||
|
trims excess pages aggressively. Any value >= 1 acts as the watermark where
|
||||||
|
trimming of allocations is initiated.
|
||||||
|
|
||||||
|
The default value is 1.
|
||||||
|
|
||||||
|
See Documentation/nommu-mmap.txt for more information.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
numa_zonelist_order
|
numa_zonelist_order
|
||||||
|
|
||||||
This sysctl is only for NUMA.
|
This sysctl is only for NUMA.
|
||||||
|
|
@ -335,34 +421,199 @@ this is causing problems for your system/application.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
nr_hugepages
|
oom_dump_tasks
|
||||||
|
|
||||||
Change the minimum size of the hugepage pool.
|
Enables a system-wide task dump (excluding kernel threads) to be
|
||||||
|
produced when the kernel performs an OOM-killing and includes such
|
||||||
|
information as pid, uid, tgid, vm size, rss, cpu, oom_adj score, and
|
||||||
|
name. This is helpful to determine why the OOM killer was invoked
|
||||||
|
and to identify the rogue task that caused it.
|
||||||
|
|
||||||
See Documentation/vm/hugetlbpage.txt
|
If this is set to zero, this information is suppressed. On very
|
||||||
|
large systems with thousands of tasks it may not be feasible to dump
|
||||||
|
the memory state information for each one. Such systems should not
|
||||||
|
be forced to incur a performance penalty in OOM conditions when the
|
||||||
|
information may not be desired.
|
||||||
|
|
||||||
|
If this is set to non-zero, this information is shown whenever the
|
||||||
|
OOM killer actually kills a memory-hogging task.
|
||||||
|
|
||||||
|
The default value is 0.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
nr_overcommit_hugepages
|
oom_kill_allocating_task
|
||||||
|
|
||||||
Change the maximum size of the hugepage pool. The maximum is
|
This enables or disables killing the OOM-triggering task in
|
||||||
nr_hugepages + nr_overcommit_hugepages.
|
out-of-memory situations.
|
||||||
|
|
||||||
See Documentation/vm/hugetlbpage.txt
|
If this is set to zero, the OOM killer will scan through the entire
|
||||||
|
tasklist and select a task based on heuristics to kill. This normally
|
||||||
|
selects a rogue memory-hogging task that frees up a large amount of
|
||||||
|
memory when killed.
|
||||||
|
|
||||||
|
If this is set to non-zero, the OOM killer simply kills the task that
|
||||||
|
triggered the out-of-memory condition. This avoids the expensive
|
||||||
|
tasklist scan.
|
||||||
|
|
||||||
|
If panic_on_oom is selected, it takes precedence over whatever value
|
||||||
|
is used in oom_kill_allocating_task.
|
||||||
|
|
||||||
|
The default value is 0.
|
||||||
|
|
||||||
==============================================================
|
==============================================================
|
||||||
|
|
||||||
nr_trim_pages
|
overcommit_memory:
|
||||||
|
|
||||||
This is available only on NOMMU kernels.
|
This value contains a flag that enables memory overcommitment.
|
||||||
|
|
||||||
This value adjusts the excess page trimming behaviour of power-of-2 aligned
|
When this flag is 0, the kernel attempts to estimate the amount
|
||||||
NOMMU mmap allocations.
|
of free memory left when userspace requests more memory.
|
||||||
|
|
||||||
A value of 0 disables trimming of allocations entirely, while a value of 1
|
When this flag is 1, the kernel pretends there is always enough
|
||||||
trims excess pages aggressively. Any value >= 1 acts as the watermark where
|
memory until it actually runs out.
|
||||||
trimming of allocations is initiated.
|
|
||||||
|
|
||||||
The default value is 1.
|
When this flag is 2, the kernel uses a "never overcommit"
|
||||||
|
policy that attempts to prevent any overcommit of memory.
|
||||||
|
|
||||||
See Documentation/nommu-mmap.txt for more information.
|
This feature can be very useful because there are a lot of
|
||||||
|
programs that malloc() huge amounts of memory "just-in-case"
|
||||||
|
and don't use much of it.
|
||||||
|
|
||||||
|
The default value is 0.
|
||||||
|
|
||||||
|
See Documentation/vm/overcommit-accounting and
|
||||||
|
security/commoncap.c::cap_vm_enough_memory() for more information.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
overcommit_ratio:
|
||||||
|
|
||||||
|
When overcommit_memory is set to 2, the committed address
|
||||||
|
space is not permitted to exceed swap plus this percentage
|
||||||
|
of physical RAM. See above.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
page-cluster
|
||||||
|
|
||||||
|
page-cluster controls the number of pages which are written to swap in
|
||||||
|
a single attempt. The swap I/O size.
|
||||||
|
|
||||||
|
It is a logarithmic value - setting it to zero means "1 page", setting
|
||||||
|
it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
|
||||||
|
|
||||||
|
The default value is three (eight pages at a time). There may be some
|
||||||
|
small benefits in tuning this to a different value if your workload is
|
||||||
|
swap-intensive.
|
||||||
|
|
||||||
|
=============================================================
|
||||||
|
|
||||||
|
panic_on_oom
|
||||||
|
|
||||||
|
This enables or disables panic on out-of-memory feature.
|
||||||
|
|
||||||
|
If this is set to 0, the kernel will kill some rogue process,
|
||||||
|
called oom_killer. Usually, oom_killer can kill rogue processes and
|
||||||
|
system will survive.
|
||||||
|
|
||||||
|
If this is set to 1, the kernel panics when out-of-memory happens.
|
||||||
|
However, if a process limits using nodes by mempolicy/cpusets,
|
||||||
|
and those nodes become memory exhaustion status, one process
|
||||||
|
may be killed by oom-killer. No panic occurs in this case.
|
||||||
|
Because other nodes' memory may be free. This means system total status
|
||||||
|
may be not fatal yet.
|
||||||
|
|
||||||
|
If this is set to 2, the kernel panics compulsorily even on the
|
||||||
|
above-mentioned.
|
||||||
|
|
||||||
|
The default value is 0.
|
||||||
|
1 and 2 are for failover of clustering. Please select either
|
||||||
|
according to your policy of failover.
|
||||||
|
|
||||||
|
=============================================================
|
||||||
|
|
||||||
|
percpu_pagelist_fraction
|
||||||
|
|
||||||
|
This is the fraction of pages at most (high mark pcp->high) in each zone that
|
||||||
|
are allocated for each per cpu page list. The min value for this is 8. It
|
||||||
|
means that we don't allow more than 1/8th of pages in each zone to be
|
||||||
|
allocated in any single per_cpu_pagelist. This entry only changes the value
|
||||||
|
of hot per cpu pagelists. User can specify a number like 100 to allocate
|
||||||
|
1/100th of each zone to each per cpu page list.
|
||||||
|
|
||||||
|
The batch value of each per cpu pagelist is also updated as a result. It is
|
||||||
|
set to pcp->high/4. The upper limit of batch is (PAGE_SHIFT * 8)
|
||||||
|
|
||||||
|
The initial value is zero. Kernel does not use this value at boot time to set
|
||||||
|
the high water marks for each per cpu page list.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
stat_interval
|
||||||
|
|
||||||
|
The time interval between which vm statistics are updated. The default
|
||||||
|
is 1 second.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
swappiness
|
||||||
|
|
||||||
|
This control is used to define how aggressive the kernel will swap
|
||||||
|
memory pages. Higher values will increase agressiveness, lower values
|
||||||
|
descrease the amount of swap.
|
||||||
|
|
||||||
|
The default value is 60.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
vfs_cache_pressure
|
||||||
|
------------------
|
||||||
|
|
||||||
|
Controls the tendency of the kernel to reclaim the memory which is used for
|
||||||
|
caching of directory and inode objects.
|
||||||
|
|
||||||
|
At the default value of vfs_cache_pressure=100 the kernel will attempt to
|
||||||
|
reclaim dentries and inodes at a "fair" rate with respect to pagecache and
|
||||||
|
swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer
|
||||||
|
to retain dentry and inode caches. Increasing vfs_cache_pressure beyond 100
|
||||||
|
causes the kernel to prefer to reclaim dentries and inodes.
|
||||||
|
|
||||||
|
==============================================================
|
||||||
|
|
||||||
|
zone_reclaim_mode:
|
||||||
|
|
||||||
|
Zone_reclaim_mode allows someone to set more or less aggressive approaches to
|
||||||
|
reclaim memory when a zone runs out of memory. If it is set to zero then no
|
||||||
|
zone reclaim occurs. Allocations will be satisfied from other zones / nodes
|
||||||
|
in the system.
|
||||||
|
|
||||||
|
This is value ORed together of
|
||||||
|
|
||||||
|
1 = Zone reclaim on
|
||||||
|
2 = Zone reclaim writes dirty pages out
|
||||||
|
4 = Zone reclaim swaps pages
|
||||||
|
|
||||||
|
zone_reclaim_mode is set during bootup to 1 if it is determined that pages
|
||||||
|
from remote zones will cause a measurable performance reduction. The
|
||||||
|
page allocator will then reclaim easily reusable pages (those page
|
||||||
|
cache pages that are currently not used) before allocating off node pages.
|
||||||
|
|
||||||
|
It may be beneficial to switch off zone reclaim if the system is
|
||||||
|
used for a file server and all of memory should be used for caching files
|
||||||
|
from disk. In that case the caching effect is more important than
|
||||||
|
data locality.
|
||||||
|
|
||||||
|
Allowing zone reclaim to write out pages stops processes that are
|
||||||
|
writing large amounts of data from dirtying pages on other nodes. Zone
|
||||||
|
reclaim will write out dirty pages if a zone fills up and so effectively
|
||||||
|
throttle the process. This may decrease the performance of a single process
|
||||||
|
since it cannot use all of system memory to buffer the outgoing writes
|
||||||
|
anymore but it preserve the memory on other nodes so that the performance
|
||||||
|
of other processes running on other nodes will not be affected.
|
||||||
|
|
||||||
|
Allowing regular swap effectively restricts allocations to the local
|
||||||
|
node unless explicitly overridden by memory policies or cpuset
|
||||||
|
configurations.
|
||||||
|
|
||||||
|
============ End of Document =================================
|
||||||
|
|
|
||||||
Loading…
Reference in a new issue