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mm, oom: add comment for why oom_adj exists

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/proc/pid/oom_adj exists solely to avoid breaking existing userspace
binaries that write to the tunable.

Add a comment in the only possible location within the kernel tree to
describe the situation and motivation for keeping it around.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2015-11-05 18:50:32 -08:00 committed by Linus Torvalds
parent c12176d336
commit b72bdfa736
1 changed files with 10 additions and 0 deletions
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10
fs/proc/base.c
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@ -1032,6 +1032,16 @@ static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
return simple_read_from_buffer(buf, count, ppos, buffer, len);
}
/*
* /proc/pid/oom_adj exists solely for backwards compatibility with previous
* kernels. The effective policy is defined by oom_score_adj, which has a
* different scale: oom_adj grew exponentially and oom_score_adj grows linearly.
* Values written to oom_adj are simply mapped linearly to oom_score_adj.
* Processes that become oom disabled via oom_adj will still be oom disabled
* with this implementation.
*
* oom_adj cannot be removed since existing userspace binaries use it.
*/
static ssize_t oom_adj_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{