From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [PATCH] mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim Date: Wed, 18 Aug 2021 10:15:24 -0400 Message-ID: References: <20210817180506.220056-1-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=rg02+w1DlkJobhoJY9bM97YQwIjcX3dhjCH/vsEFgP0=; b=IJM3/57oMfrwBGTxX1IHTSufxeq6P3Ds6XRZvE9DZaQYu6SrVcwDRerEYF25qu7X1B P60N9RrgrRNag8tqLyPwd2wzaLi9O55qN9diwm9sZAtemcAodh0vkx7GORHTW9R5W2LY rV/W0SNTLdFLW8cLcW0Qu/6ySAJpxaO6I9bAxGJSjR5kQXqiY7nMpO/wVGbIlV0HDfjw dYuz+g7ZxYVhUxmQisLCpNH+9kMNrqw8fYLGpqtTiUzPzHScZLMpGUR7odgvREoOGyvq uG3PAzekn0lUz/hG2/KBgIhbNa18vFUOGqnNMOmaodYK+aTh4+ylfiWpcrP7Zlm5Pd0x G6kA== Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Roman Gushchin Cc: Andrew Morton , Leon Yang , Chris Down , Michal Hocko , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org On Tue, Aug 17, 2021 at 12:45:18PM -0700, Roman Gushchin wrote: > On Tue, Aug 17, 2021 at 02:05:06PM -0400, Johannes Weiner wrote: > > We've noticed occasional OOM killing when memory.low settings are in > > effect for cgroups. This is unexpected and undesirable as memory.low > > is supposed to express non-OOMing memory priorities between cgroups. > > > > The reason for this is proportional memory.low reclaim. When cgroups > > are below their memory.low threshold, reclaim passes them over in the > > first round, and then retries if it couldn't find pages anywhere else. > > But when cgroups are slighly above their memory.low setting, page scan > > force is scaled down and diminished in proportion to the overage, to > > the point where it can cause reclaim to fail as well - only in that > > case we currently don't retry, and instead trigger OOM. > > > > To fix this, hook proportional reclaim into the same retry logic we > > have in place for when cgroups are skipped entirely. This way if > > reclaim fails and some cgroups were scanned with dimished pressure, > > we'll try another full-force cycle before giving up and OOMing. > > > > Reported-by: Leon Yang > > Signed-off-by: Johannes Weiner > > Acked-by: Roman Gushchin Thank you. > I guess it's a stable material, so maybe adding: > Fixes: 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim") Yes, that Fixes makes sense. Plus: Cc: # 5.4+ I initially didn't tag it because the issue is over two years old and we've had no other reports of this. But thinking about it, it's probably more a lack of users rather than severity. At FB we only noticed with a recent rollout of memory_recursiveprot (8a931f801340c2be10552c7b5622d5f4852f3a36) because we didn't have working memory.low configurations before that. But now that we do notice, it's a problem worth fixing. So yes, stable makes sense. Thanks.