Hi, 在 2023/05/31 23:42, Xiao Ni 写道:
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?
Just a simple fio script to test 4 ramdisk/loop 16thread 4k write in my VM, and I didn't notice regression, however, I didn't run benchmarks yet, I don't have such physical environment to test performance for now... I'll definitely run some performance tests in physical evironment later. Thanks, Kuai
Regards Xiaoreturn 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.
