From 21bd9a68fef47c4f0e951be9a6fac9745cee1bab Mon Sep 17 00:00:00 2001 From: Jack Wang Date: Wed, 5 Jul 2023 13:32:27 +0200 Subject: [PATCH] md/raid1: Avoid lock contention from wake_up() wake_up is called unconditionally in a few paths such as make_request(), which cause lock contention under high concurrency workload like below raid1_end_write_request wake_up __wake_up_common_lock spin_lock_irqsave Improve performance by only call wake_up() if waitqueue is not empty Fio test script: [global] name=random reads and writes ioengine=libaio direct=1 readwrite=randrw rwmixread=70 iodepth=64 buffered=0 filename=/dev/md0 size=1G runtime=30 time_based randrepeat=0 norandommap refill_buffers ramp_time=10 bs=4k numjobs=400 group_reporting=1 [job1] Test result with 2 ramdisk in raid1 on a Intel Broadwell 56 cores server. Before this patch With this patch READ BW=4621MB/s BW=7337MB/s WRITE BW=1980MB/s BW=3144MB/s The patch is inspired by Yu Kuai's change for raid10: https://lore.kernel.org/r/20230621105728.1268542-1-yukuai1@huaweicloud.com Cc: Yu Kuai Signed-off-by: Jack Wang Reviewed-by: Yu Kuai Link: https://lore.kernel.org/r/20230705113227.148494-1-jinpu.wang@ionos.com Signed-off-by: Song Liu --- drivers/md/raid1.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index a68c9cc..23d2119 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -789,11 +789,17 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect return best_disk; } +static void wake_up_barrier(struct r1conf *conf) +{ + if (wq_has_sleeper(&conf->wait_barrier)) + wake_up(&conf->wait_barrier); +} + static void flush_bio_list(struct r1conf *conf, struct bio *bio) { /* flush any pending bitmap writes to disk before proceeding w/ I/O */ raid1_prepare_flush_writes(conf->mddev->bitmap); - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); while (bio) { /* submit pending writes */ struct bio *next = bio->bi_next; @@ -970,7 +976,7 @@ static bool _wait_barrier(struct r1conf *conf, int idx, bool nowait) * In case freeze_array() is waiting for * get_unqueued_pending() == extra */ - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); /* Wait for the barrier in same barrier unit bucket to drop. */ /* Return false when nowait flag is set */ @@ -1013,7 +1019,7 @@ static bool wait_read_barrier(struct r1conf *conf, sector_t sector_nr, bool nowa * In case freeze_array() is waiting for * get_unqueued_pending() == extra */ - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); /* Wait for array to be unfrozen */ /* Return false when nowait flag is set */ @@ -1042,7 +1048,7 @@ static bool wait_barrier(struct r1conf *conf, sector_t sector_nr, bool nowait) static void _allow_barrier(struct r1conf *conf, int idx) { atomic_dec(&conf->nr_pending[idx]); - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); } static void allow_barrier(struct r1conf *conf, sector_t sector_nr) @@ -1171,7 +1177,7 @@ static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule) spin_lock_irq(&conf->device_lock); bio_list_merge(&conf->pending_bio_list, &plug->pending); spin_unlock_irq(&conf->device_lock); - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); md_wakeup_thread(mddev->thread); kfree(plug); return; @@ -1574,7 +1580,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio, r1_bio_write_done(r1_bio); /* In case raid1d snuck in to freeze_array */ - wake_up(&conf->wait_barrier); + wake_up_barrier(conf); } static bool raid1_make_request(struct mddev *mddev, struct bio *bio) -- 2.7.4