From: David Rientjes Date: Fri, 6 Nov 2015 02:50:32 +0000 (-0800) Subject: mm, oom: add comment for why oom_adj exists X-Git-Tag: v4.9.8~3261^2~24 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b72bdfa73603f2f81fbac651b9ae36807e877752;p=platform%2Fkernel%2Flinux-rpi3.git 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/proc/base.c b/fs/proc/base.c index 29595af..bd3e9e6 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) {