On Mon, May 29, 2023 at 9:14 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
>
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> bio can be added to plug infinitely, and following writeback test can
> trigger huge amount of plugged bio:
>
> Test script:
> modprobe brd rd_nr=4 rd_size=10485760
> mdadm -CR /dev/md0 -l10 -n4 /dev/ram[0123] --assume-clean --bitmap=internal
> echo 0 > /proc/sys/vm/dirty_background_ratio
> fio -filename=/dev/md0 -ioengine=libaio -rw=write -bs=4k -numjobs=1 -iodepth=128 -name=test
>
> Test result:
> Monitor /sys/block/md0/inflight will found that inflight keep increasing
> until fio finish writing, after running for about 2 minutes:
>
> [root@fedora ~]# cat /sys/block/md0/inflight
> 0 4474191
>
> Fix the problem by limiting the number of plugged bio based on the number
> of copies for original bio.
>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
> drivers/md/raid1-10.c | 9 ++++++++-
> drivers/md/raid1.c | 2 +-
> drivers/md/raid10.c | 2 +-
> 3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
> index 17e55c1fd5a1..bb1e23b66c45 100644
> --- a/drivers/md/raid1-10.c
> +++ b/drivers/md/raid1-10.c
> @@ -21,6 +21,7 @@
> #define IO_MADE_GOOD ((struct bio *)2)
>
> #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
> +#define MAX_PLUG_BIO 32
>
> /* for managing resync I/O pages */
> struct resync_pages {
> @@ -31,6 +32,7 @@ struct resync_pages {
> struct raid1_plug_cb {
> struct blk_plug_cb cb;
> struct bio_list pending;
> + unsigned int count;
> };
>
> static void rbio_pool_free(void *rbio, void *data)
> @@ -128,7 +130,7 @@ static inline void raid1_submit_write(struct bio *bio)
> }
>
> static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
> - blk_plug_cb_fn unplug)
> + blk_plug_cb_fn unplug, int copies)
> {
> struct raid1_plug_cb *plug = NULL;
> struct blk_plug_cb *cb;
> @@ -148,6 +150,11 @@ static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
>
> plug = container_of(cb, struct raid1_plug_cb, cb);
> bio_list_add(&plug->pending, bio);
> + if (++plug->count / MAX_PLUG_BIO >= copies) {
> + list_del(&cb->list);
> + cb->callback(cb, false);
> + }
> +
It doesn't need this line here.
Have you done some performance tests with this patch set?
Regards
Xiao
>
> return true;
> }
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 006620fed595..dc89a1c4b1f1 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1562,7 +1562,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
> r1_bio->sector);
> /* flush_pending_writes() needs access to the rdev so...*/
> mbio->bi_bdev = (void *)rdev;
> - if (!raid1_add_bio_to_plug(mddev, mbio, raid1_unplug)) {
> + if (!raid1_add_bio_to_plug(mddev, mbio, raid1_unplug, disks)) {
> spin_lock_irqsave(&conf->device_lock, flags);
> bio_list_add(&conf->pending_bio_list, mbio);
> spin_unlock_irqrestore(&conf->device_lock, flags);
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index fb22cfe94d32..9237dbeb07ba 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -1306,7 +1306,7 @@ static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
>
> atomic_inc(&r10_bio->remaining);
>
> - if (!raid1_add_bio_to_plug(mddev, mbio, raid10_unplug)) {
> + if (!raid1_add_bio_to_plug(mddev, mbio, raid10_unplug, conf->copies)) {
> spin_lock_irqsave(&conf->device_lock, flags);
> bio_list_add(&conf->pending_bio_list, mbio);
> spin_unlock_irqrestore(&conf->device_lock, flags);
> --
> 2.39.2
>
