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authorDavid Rientjes <rientjes@google.com>2015-11-05 18:50:32 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-05 19:34:48 -0800
commitb72bdfa73603f2f81fbac651b9ae36807e877752 (patch)
treed302a8fb0e69169ef9e0749918ab6f0fd26ac2a9 /fs/proc
parentc12176d3368b9b36ae484d323d41e94be26f9b65 (diff)
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mm, oom: add comment for why oom_adj exists
/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>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/base.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 29595af32866..bd3e9e68125b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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)
{