Re: [PATCH] memcg, kmem: do not fail __GFP_NOFAIL charges

Michal Hocko
2019-09-11T12:00:08Z

On Mon 09-09-19 13:22:45, Michal Hocko wrote:
> On Fri 06-09-19 11:24:55, Shakeel Butt wrote:
[...]
> > I wonder what has changed since
> > <http://lkml.kernel.org/r/20180525185501.82098-1-shakeelb@google.com/>.
>
> I have completely forgot about that one. It seems that we have just
> repeated the same discussion again. This time we have a poor user who
> actually enabled the kmem limit.
>
> I guess there was no real objection to the change back then. The primary
> discussion revolved around the fact that the accounting will stay broken
> even when this particular part was fixed. Considering this leads to easy
> to trigger crash (with the limit enabled) then I guess we should just
> make it less broken and backport to stable trees and have a serious
> discussion about discontinuing of the limit. Start by simply failing to
> set any limit in the current upstream kernels.

Any more concerns/objections to the patch? I can add a reference to your
earlier post Shakeel if you want or to credit you the way you prefer.

Also are there any objections to start deprecating process of kmem
limit? I would see it in two stages
- 1st warn in the kernel log
pr_warn("kmem.limit_in_bytes is deprecated and will be removed.
"Please report your usecase to linux-mm@kvack.org if you "
"depend on this functionality."
- 2nd fail any write to kmem.limit_in_bytes
- 3rd remove the control file completely
--
Michal Hocko
SUSE Labs