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Wed, 01 Apr 2026 19:56:15 -0700 (PDT) Received: from KASONG-MC4 ([43.132.141.25]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b27478b84esm10880025ad.32.2026.04.01.19.56.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 19:56:15 -0700 (PDT) Date: Thu, 2 Apr 2026 10:56:07 +0800 From: Kairui Song To: Shakeel Butt Cc: kasong@tencent.com, linux-mm@kvack.org, Andrew Morton , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Qi Zheng , Lorenzo Stoakes , Barry Song , David Stevens , Chen Ridong , Leno Hou , Yafang Shao , Yu Zhao , Zicheng Wang , Kalesh Singh , Suren Baghdasaryan , Chris Li , Vernon Yang , linux-kernel@vger.kernel.org, Qi Zheng , Baolin Wang Subject: Re: [PATCH v2 12/12] mm/vmscan: unify writeback reclaim statistic and throttling Message-ID: References: <20260329-mglru-reclaim-v2-0-b53a3678513c@tencent.com> <20260329-mglru-reclaim-v2-12-b53a3678513c@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E663D20008 X-Stat-Signature: 7eufh1n9az4htb9idcpr3c3wieh3ey1m X-HE-Tag: 1775098576-180193 X-HE-Meta: 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 O44dmrNu 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 01, 2026 at 07:39:03PM +0800, Shakeel Butt wrote: > On Sun, Mar 29, 2026 at 03:52:38AM +0800, Kairui Song via B4 Relay wrote: > > From: Kairui Song > > > > Currently MGLRU and non-MGLRU handle the reclaim statistic and > > writeback handling very differently, especially throttling. > > Basically MGLRU just ignored the throttling part. > > > > Let's just unify this part, use a helper to deduplicate the code > > so both setups will share the same behavior. Also remove the > > folio_clear_reclaim in isolate_folio which was actively invalidating > > the congestion control. PG_reclaim is now handled by shrink_folio_list, > > keeping it in isolate_folio is not helpful. > > > > Test using following reproducer using bash: > > > > echo "Setup a slow device using dm delay" > > dd if=/dev/zero of=/var/tmp/backing bs=1M count=2048 > > LOOP=$(losetup --show -f /var/tmp/backing) > > mkfs.ext4 -q $LOOP > > echo "0 $(blockdev --getsz $LOOP) delay $LOOP 0 0 $LOOP 0 1000" | \ > > dmsetup create slow_dev > > mkdir -p /mnt/slow && mount /dev/mapper/slow_dev /mnt/slow > > > > echo "Start writeback pressure" > > sync && echo 3 > /proc/sys/vm/drop_caches > > mkdir /sys/fs/cgroup/test_wb > > echo 128M > /sys/fs/cgroup/test_wb/memory.max > > (echo $BASHPID > /sys/fs/cgroup/test_wb/cgroup.procs && \ > > dd if=/dev/zero of=/mnt/slow/testfile bs=1M count=192) > > > > echo "Clean up" > > echo "0 $(blockdev --getsz $LOOP) error" | dmsetup load slow_dev > > dmsetup resume slow_dev > > umount -l /mnt/slow && sync > > dmsetup remove slow_dev > > > > Before this commit, `dd` will get OOM killed immediately if > > MGLRU is enabled. Classic LRU is fine. > > > > After this commit, congestion control is now effective and no more > > What do you mean by congestion control here? This particular case demostrated here is VMSCAN_THROTTLE_CONGESTED so I described it as "congestion control", may I'll just say throttling to avoid confusion, it's not limited to that. > > > spin on LRU or premature OOM. > > > > Stress test on other workloads also looking good. > > > > Suggested-by: Chen Ridong > > Signed-off-by: Kairui Song > > There is still differences for global and kswapd reclaim in the shrink_node() > like kswapd throttling and congestion state management and throttling. Any plan > to unify them? Of course. Let fix it step by step, this series is pretty long already. I originally plan to put this patch in a later series, but as Ridong pointed out leaving these counter updated but unused looks really ugly. And this fix is clean and easily to understand I think.