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b=XQYKTxfMDs2yIB6CWGVZiSp5f5BHo9jhEr9E32RgdQuoefyg7epRcIq51oEJggqu0uAXyQRA/5N3ttRgh/7ilsrGpKCu32YnVENGa2JfAYzLGV10948f3oc9L2QmXzeNiRGKw9OPwzDrSvhKLvF17KNo4s0pUwKafo+RKpsUWA8= 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 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 X-Rspamd-Queue-Id: EAD62180005 X-Stat-Signature: zka4upejyotuy3fezi6gbec14t1q3nwt X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774514489-572486 X-HE-Meta: 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 xsCBoE+6 MxHPRugm/SguYpYKnMJeMQLa6PGSbVFMUpPq8ARxXU9KNKVmgnrZLY8WMDftNa2d/YguS/Xz4T+hW++v9v8EQ+D+DXNI6WE9yExhl1OcmcQzDyznhQ++Awsy6e7l5hCZ2bCbyRyGLlEMQnfUS7zvpRaryeXEI5zRnfSg3x9Rp0w5LlY+LhzK5S+WInUp442iKQgpg47ymFqR0mMmJpmZ7w6zY8gUWEgCn5TbwughbQ3nbbRUYcT8kWEOpEK1oI5HEv/h+8jhWhEx2cc5nem0H0HIsz1HZqsFioHV1+9q9fZDGG+9oCRIrbQE0ITnAGuZeTtvDbD1+qQ6yEFsJJJlBVoBR3yEblHSISdsICA6N0WWt/viMONey5Lsmdw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 >>