path: root/Documentation
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authorDavid Rientjes <rientjes@google.com>2010-11-11 14:05:18 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-11-12 07:55:31 -0800
commit203f40a5a030ed4048cd40e3bd9ab5df6c5df589 (patch)
tree5829b47ddea21cd98901a0f59e655477dc8cdfc9 /Documentation
parent1dce071e18b7264457d17c0dec4c7e430bfaee7d (diff)
oom: document obsolete oom_adj tunable
/proc/pid/oom_adj was deprecated in August 2010 with the introduction of the new oom killer heuristic. This patch copies the Documentation/feature-removal-schedule.txt entry for this tunable to the Documentation/ABI/obsolete directory so nobody misses it. Signed-off-by: David Rientjes <rientjes@google.com> Reported-by: 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')
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/ABI/obsolete/proc-pid-oom_adj b/Documentation/ABI/obsolete/proc-pid-oom_adj
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index 00000000000..cf63f264ce0
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+++ b/Documentation/ABI/obsolete/proc-pid-oom_adj
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+What: /proc/<pid>/oom_adj
+When: August 2012
+Why: /proc/<pid>/oom_adj allows userspace to influence the oom killer's
+ badness heuristic used to determine which task to kill when the kernel
+ is out of memory.
+ The badness heuristic has since been rewritten since the introduction of
+ this tunable such that its meaning is deprecated. The value was
+ implemented as a bitshift on a score generated by the badness()
+ function that did not have any precise units of measure. With the
+ rewrite, the score is given as a proportion of available memory to the
+ task allocating pages, so using a bitshift which grows the score
+ exponentially is, thus, impossible to tune with fine granularity.
+ A much more powerful interface, /proc/<pid>/oom_score_adj, was
+ introduced with the oom killer rewrite that allows users to increase or
+ decrease the badness() score linearly. This interface will replace
+ /proc/<pid>/oom_adj.
+ A warning will be emitted to the kernel log if an application uses this
+ deprecated interface. After it is printed once, future warnings will be
+ suppressed until the kernel is rebooted.