Re: [PATCH v3 14/14] mm/vmscan: unify writeback reclaim statistic and throttling

[Baolin Wang]

On 4/3/26 2:53 AM, Kairui Song via B4 Relay wrote:
> From: Kairui Song <kasong@xxxxxxxxxxx>
>
> 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.
>
> 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, throttling is now effective and no more spin on
> LRU or premature OOM. Stress test on other workloads also looking good.
>
> Global throttling is not here yet, we will fix that separately later.
>
> Suggested-by: Chen Ridong <chenridong@xxxxxxxxxxxxxxx>
> Tested-by: Leno Hou <lenohou@xxxxxxxxx>
> Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>