From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 013DB8BF3 for ; Sun, 4 Feb 2024 07:20:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707031238; cv=none; b=mQHELOSOWwbCj1oEW2tvayv7PFYpGHsYhIIlegoMdoJC/au32cABaVSc6UtH8vZmIY4SsCNjlkTtmoi9hf4PuWpWJ5xuTnC50djilEOyImDZqZ4oir9+CwbzQzSiepNnqRIcr2HyAZrQRwGMnSJDp4iWI3oS4svR2c1KRZxILeo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707031238; c=relaxed/simple; bh=iE+Z+0JKhcnDhv9VEzVDkM5Whx77z2KOdTu5qGNUaug=; h=Date:To:From:Subject:Message-Id; b=tWT8Wmedb39MdaL1I1Q9VLdE63zmyK8drrQGD8GDi8q1BJaNnFuJaRkXmsdjptA9eMi7HHoOFxcZ+QAV+qIPX/YiQcAe99SEPRqwHQcXLeks3ntCIPOeypAQ/GQPE9/Mgb/S8kx2+0gtvakGSM5Qk9yAcr8ZN/lWGYtXwBZSVtQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Tlod62pd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Tlod62pd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B093DC433F1; Sun, 4 Feb 2024 07:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1707031237; bh=iE+Z+0JKhcnDhv9VEzVDkM5Whx77z2KOdTu5qGNUaug=; h=Date:To:From:Subject:From; b=Tlod62pdVD0Z0ICU/aF6W5arETtefb58xTpR1tmKYuRZ4u82TWKTW4kW5WVqfbbml pYSJb8O0rNtbsSMScPj+c/07u1ZTirgeL1JAqR2H40dMZcgwZaFB8wqr7bz56CbIAZ GAK/y4BTuTYDU+LfATHkZR+Tk+LCJjj1RX8crCDw= Date: Sat, 03 Feb 2024 23:20:37 -0800 To: mm-commits@vger.kernel.org,yuzhao@google.com,yosryahmed@google.com,yangyifei03@kuaishou.com,songmuchun@bytedance.com,shakeelb@google.com,roman.gushchin@linux.dev,mkoutny@suse.com,mhocko@suse.com,hannes@cmpxchg.org,tjmercier@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-memcg-use-larger-batches-for-proactive-reclaim.patch added to mm-unstable branch Message-Id: <20240204072037.B093DC433F1@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: memcg: use larger batches for proactive reclaim has been added to the -mm mm-unstable branch. Its filename is mm-memcg-use-larger-batches-for-proactive-reclaim.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-use-larger-batches-for-proactive-reclaim.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: "T.J. Mercier" Subject: mm: memcg: use larger batches for proactive reclaim Date: Fri, 2 Feb 2024 23:38:54 +0000 Before 388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive reclaim") we passed the number of pages for the reclaim request directly to try_to_free_mem_cgroup_pages, which could lead to significant overreclaim. After 0388536ac291 the number of pages was limited to a maximum 32 (SWAP_CLUSTER_MAX) to reduce the amount of overreclaim. However such a small batch size caused a regression in reclaim performance due to many more reclaim start/stop cycles inside memory_reclaim. Reclaim tries to balance nr_to_reclaim fidelity with fairness across nodes and cgroups over which the pages are spread. As such, the bigger the request, the bigger the absolute overreclaim error. Historic in-kernel users of reclaim have used fixed, small sized requests to approach an appropriate reclaim rate over time. When we reclaim a user request of arbitrary size, use decaying batch sizes to manage error while maintaining reasonable throughput. root - full reclaim pages/sec time (sec) pre-0388536ac291 : 68047 10.46 post-0388536ac291 : 13742 inf (reclaim-reclaimed)/4 : 67352 10.51 /uid_0 - 1G reclaim pages/sec time (sec) overreclaim (MiB) pre-0388536ac291 : 258822 1.12 107.8 post-0388536ac291 : 105174 2.49 3.5 (reclaim-reclaimed)/4 : 233396 1.12 -7.4 /uid_0 - full reclaim pages/sec time (sec) pre-0388536ac291 : 72334 7.09 post-0388536ac291 : 38105 14.45 (reclaim-reclaimed)/4 : 72914 6.96 Link: https://lkml.kernel.org/r/20240202233855.1236422-1-tjmercier@google.com Fixes: 0388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive re= claim") Signed-off-by: T.J. Mercier Reviewed-by: Yosry Ahmed Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Roman Gushchin Cc: Shakeel Butt Cc: Muchun Song Cc: Efly Young Cc: Michal Koutny Cc: Yu Zhao Signed-off-by: Andrew Morton --- mm/memcontrol.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/memcontrol.c~mm-memcg-use-larger-batches-for-proactive-reclaim +++ a/mm/memcontrol.c @@ -6994,9 +6994,11 @@ static ssize_t memory_reclaim(struct ker if (!nr_retries) lru_add_drain_all(); + /* Will converge on zero, but reclaim enforces a minimum */ + unsigned long batch_size = (nr_to_reclaim - nr_reclaimed) / 4; + reclaimed = try_to_free_mem_cgroup_pages(memcg, - min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX), - GFP_KERNEL, reclaim_options); + batch_size, GFP_KERNEL, reclaim_options); if (!reclaimed && !nr_retries--) return -EAGAIN; _ Patches currently in -mm which might be from tjmercier@google.com are mm-memcg-dont-periodically-flush-stats-when-memcg-is-disabled.patch mm-memcg-use-larger-batches-for-proactive-reclaim.patch