Messages in this thread | | | Date | Thu, 5 Nov 2015 11:28:41 +0100 | From | Michal Hocko <> | Subject | Re: [patch] mm, oom: add comment for why oom_adj exists |
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On Wed 04-11-15 12:32:14, David Rientjes wrote: > /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.
I am not sure this is really needed but it certainly is not harmful. If this is a way to suppress any attempts for changes like http://lkml.kernel.org/r/1f80189385e540c2a5b2747a7a265d8c%40SHMBX01.spreadtrum.com then it does not explain why those are not desirable.
> Signed-off-by: David Rientjes <rientjes@google.com> > --- > fs/proc/base.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > --- 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.
This is a bit strong wording. I think the knob can be removed in the future.
* oom_adj is kept for compatibility reasons. There are still few * projects which use oom_adj only. We have tried to convert all of them * which could be found but it will take some time until all those changes * bubble up to all users. We might try to remove the knob in few years * if the situtation changes.
> + */ > static ssize_t oom_adj_write(struct file *file, const char __user *buf, > size_t count, loff_t *ppos) > {
-- Michal Hocko SUSE Labs
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