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authorJerome Marchand <jmarchan@redhat.com>2014-01-21 15:49:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-21 16:19:44 -0800
commit49f0ce5f92321cdcf741e35f385669a421013cb7 (patch)
treed41c5a2283b32be69840cb8722ffd8cd8c38a1b0 /Documentation
parentaec6a8889a98a0cd58357cd0937a25189908f191 (diff)
downloadlinux-49f0ce5f92321cdcf741e35f385669a421013cb7.tar.bz2
mm: add overcommit_kbytes sysctl variable
Some applications that run on HPC clusters are designed around the availability of RAM and the overcommit ratio is fine tuned to get the maximum usage of memory without swapping. With growing memory, the 1%-of-all-RAM grain provided by overcommit_ratio has become too coarse for these workload (on a 2TB machine it represents no less than 20GB). This patch adds the new overcommit_kbytes sysctl variable that allow a much finer grain. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix nommu build] Signed-off-by: Jerome Marchand <jmarchan@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/sysctl/vm.txt12
-rw-r--r--Documentation/vm/overcommit-accounting7
2 files changed, 16 insertions, 3 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 1fbd4eb7b64a..9f5481bdc5a4 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -47,6 +47,7 @@ Currently, these files are in /proc/sys/vm:
- numa_zonelist_order
- oom_dump_tasks
- oom_kill_allocating_task
+- overcommit_kbytes
- overcommit_memory
- overcommit_ratio
- page-cluster
@@ -574,6 +575,17 @@ The default value is 0.
==============================================================
+overcommit_kbytes:
+
+When overcommit_memory is set to 2, the committed address space is not
+permitted to exceed swap plus this amount of physical RAM. See below.
+
+Note: overcommit_kbytes is the counterpart of overcommit_ratio. Only one
+of them may be specified at a time. Setting one disables the other (which
+then appears as 0 when read).
+
+==============================================================
+
overcommit_memory:
This value contains a flag that enables memory overcommitment.
diff --git a/Documentation/vm/overcommit-accounting b/Documentation/vm/overcommit-accounting
index 8eaa2fc4b8fa..cbfaaa674118 100644
--- a/Documentation/vm/overcommit-accounting
+++ b/Documentation/vm/overcommit-accounting
@@ -14,8 +14,8 @@ The Linux kernel supports the following overcommit handling modes
2 - Don't overcommit. The total address space commit
for the system is not permitted to exceed swap + a
- configurable percentage (default is 50) of physical RAM.
- Depending on the percentage you use, in most situations
+ configurable amount (default is 50%) of physical RAM.
+ Depending on the amount you use, in most situations
this means a process will not be killed while accessing
pages but will receive errors on memory allocation as
appropriate.
@@ -26,7 +26,8 @@ The Linux kernel supports the following overcommit handling modes
The overcommit policy is set via the sysctl `vm.overcommit_memory'.
-The overcommit percentage is set via `vm.overcommit_ratio'.
+The overcommit amount can be set via `vm.overcommit_ratio' (percentage)
+or `vm.overcommit_kbytes' (absolute value).
The current overcommit limit and amount committed are viewable in
/proc/meminfo as CommitLimit and Committed_AS respectively.