From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) (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 CD6DA25776 for ; Thu, 26 Mar 2026 08:46:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.113 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774514811; cv=none; b=dZ+QfaHY5k0ABa6i/mW48/bhZFbNTk3pfl+ZG/2uuHaol3dMkyMk7nDIJPop3OdhUdczyJicjm/q11L6QdQXeO4SzrpmgaPgtIsPmulkv1G6YIkCM6FM5gvaxzkaDOs4w5yfTsDKxmQWRRUP5ef5rVaNMso6onZCV/atkImrX6E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774514811; c=relaxed/simple; bh=F+wpG+EWzXI/woYQUtxDjjHGC1zeCCjQ3iKoqLoV4HY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CYh4sErY327m4Tx1CVBK58o51UqpD/mfj3oREbhe1hXi/d5ND0/Ej3QiU4v5IYR/5TcucoNyE7xdz9S1qSVj916W6ZdWx9oTkGE/v8AFzAxnt73jqYT/AvuF8yTpELSy88443lUm39NmGYynvo2jYnY7YoQ1Qj83UpHGMHo5W5U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=QLcWG8Vt; arc=none smtp.client-ip=115.124.30.113 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="QLcWG8Vt" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1774514806; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=S+d6Cp7V+ffV/ZBZMslYlaeNUy1XXkPL+l/jdknO7xE=; b=QLcWG8Vtv5wJr+3lGKoDBcOuihJRtODhty9vdOfsq0fiqyUerS3GRmz2QAXVhFBYEl2Ue/VULVMjV5rR9OoAMupnl1WgOd7alfIDY12QkoM5CRlqV2JzG2HQOe7Nx9nyydXIPAe3UqPNFobREkwa8/o3ENk7Aao8/ceE2GB3f58= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0X.kdTKZ_1774514485; Received: from 30.74.144.123(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X.kdTKZ_1774514485 cluster:ay36) by smtp.aliyun-inc.com; Thu, 26 Mar 2026 16:41:26 +0800 Message-ID: Date: Thu, 26 Mar 2026 16:41:25 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, kasong@tencent.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/26/26 1:04 PM, Barry Song wrote: > On Wed, Mar 25, 2026 at 7:51 PM Baolin Wang > wrote: >> >> The balance_dirty_pages() won't do the dirty folios throttling on cgroupv1. >> See commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writeback >> on traditional hierarchies"). >> >> Moreover, after commit 6b0dfabb3555 ("fs: Remove aops->writepage"), we no >> longer attempt to write back filesystem folios through reclaim. >> >> On large memory systems, the flusher may not be able to write back quickly >> enough. Consequently, MGLRU will encounter many folios that are already >> under writeback. Since we cannot reclaim these dirty folios, the system >> may run out of memory and trigger the OOM killer. >> >> Hence, for cgroup v1, let's throttle reclaim after waking up the flusher, >> which is similar to commit 81a70c21d917 ("mm/cgroup/reclaim: fix dirty >> pages throttling on cgroup v1"), to avoid unnecessary OOM. >> >> The following test program can easily reproduce the OOM issue. With this patch >> applied, the test passes successfully. >> >> $mkdir /sys/fs/cgroup/memory/test >> $echo 256M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes >> $echo $$ > /sys/fs/cgroup/memory/test/cgroup.procs >> $dd if=/dev/zero of=/mnt/data.bin bs=1M count=800 >> >> Signed-off-by: Baolin Wang > > LGTM, > > Reviewed-by: Barry Song Thanks. > Maybe we can extract a common inline helper to avoid the copy-paste duplication. Kairui is planning further optimizations here (including using a helper) [1], so it might be better to leave that for his series. For this patch, I intend it to be a standalone fix, and I will add the Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation") tag. [1] https://lore.kernel.org/all/20260318-mglru-reclaim-v1-7-2c46f9eb0508@tencent.com/ >> --- >> mm/vmscan.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 33287ba4a500..a9648269fae8 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -5036,9 +5036,20 @@ static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) >> * If too many file cache in the coldest generation can't be evicted >> * due to being dirty, wake up the flusher. >> */ >> - if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty == sc->nr.file_taken) >> + if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty == sc->nr.file_taken) { >> + struct pglist_data *pgdat = lruvec_pgdat(lruvec); >> + >> wakeup_flusher_threads(WB_REASON_VMSCAN); >> >> + /* >> + * For cgroupv1 dirty throttling is achieved by waking up >> + * the kernel flusher here and later waiting on folios >> + * which are in writeback to finish (see shrink_folio_list()). >> + */ >> + if (!writeback_throttling_sane(sc)) >> + reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); >> + } >> + >> /* whether this lruvec should be rotated */ >> return nr_to_scan < 0; >> } >> -- >> 2.47.3 >>