lkml.org 
[lkml]   [2022]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 2/4] md/raid10: prevent unnecessary calls to wake_up() in fast path
From
Date
在 2022/09/14 9:49, Yu Kuai 写道:
> From: Yu Kuai <yukuai3@huawei.com>
>
> Currently, wake_up() is called unconditionally in fast path such as
> raid10_make_request(), which will cause lock contention under high
> concurrency:
>
> raid10_make_request
> wake_up
> __wake_up_common_lock
> spin_lock_irqsave
>
> Improve performance by only call wake_up() if waitqueue is not empty.
>
Hi,

I'm replacing all the wake_up() here, currently I'm not quite sure it's
OK, "conf->wait_barrier" is used for many purpose.

Perhaps should I just replace host path here? (raid10_make_request
and allow_barrier().

Thanks,
Kuai

> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
> drivers/md/raid10.c | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 56458a53043d..0edcd98461fe 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -274,6 +274,12 @@ static void put_buf(struct r10bio *r10_bio)
> lower_barrier(conf);
> }
>
> +static void wake_up_barrier(struct r10conf *conf)
> +{
> + if (wq_has_sleeper(&conf->wait_barrier))
> + wake_up(&conf->wait_barrier);
> +}
> +
> static void reschedule_retry(struct r10bio *r10_bio)
> {
> unsigned long flags;
> @@ -286,7 +292,7 @@ static void reschedule_retry(struct r10bio *r10_bio)
> spin_unlock_irqrestore(&conf->device_lock, flags);
>
> /* wake up frozen array... */
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
>
> md_wakeup_thread(mddev->thread);
> }
> @@ -884,7 +890,7 @@ static void flush_pending_writes(struct r10conf *conf)
> /* flush any pending bitmap writes to disk
> * before proceeding w/ I/O */
> md_bitmap_unplug(conf->mddev->bitmap);
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
>
> while (bio) { /* submit pending writes */
> struct bio *next = bio->bi_next;
> @@ -954,7 +960,7 @@ static void lower_barrier(struct r10conf *conf)
> spin_lock_irqsave(&conf->resync_lock, flags);
> conf->barrier--;
> spin_unlock_irqrestore(&conf->resync_lock, flags);
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> }
>
> static bool stop_waiting_barrier(struct r10conf *conf)
> @@ -1004,7 +1010,7 @@ static bool wait_barrier(struct r10conf *conf, bool nowait)
> conf->nr_waiting--;
> }
> if (!conf->nr_waiting)
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> }
> /* Only increment nr_pending when we wait */
> if (ret)
> @@ -1017,7 +1023,7 @@ static void allow_barrier(struct r10conf *conf)
> {
> if ((atomic_dec_and_test(&conf->nr_pending)) ||
> (conf->array_freeze_pending))
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> }
>
> static void freeze_array(struct r10conf *conf, int extra)
> @@ -1053,7 +1059,7 @@ static void unfreeze_array(struct r10conf *conf)
> spin_lock_irq(&conf->resync_lock);
> conf->barrier--;
> conf->nr_waiting--;
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> spin_unlock_irq(&conf->resync_lock);
> }
>
> @@ -1078,7 +1084,7 @@ static void raid10_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;
> @@ -1087,7 +1093,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
> /* we aren't scheduling, so we can do the write-out directly. */
> bio = bio_list_get(&plug->pending);
> md_bitmap_unplug(mddev->bitmap);
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
>
> while (bio) { /* submit pending writes */
> struct bio *next = bio->bi_next;
> @@ -1893,7 +1899,7 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
> __make_request(mddev, bio, sectors);
>
> /* In case raid10d snuck in to freeze_array */
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> return true;
> }
>
> @@ -3040,7 +3046,7 @@ static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
> * In case freeze_array() is waiting for condition
> * nr_pending == nr_queued + extra to be true.
> */
> - wake_up(&conf->wait_barrier);
> + wake_up_barrier(conf);
> md_wakeup_thread(conf->mddev->thread);
> } else {
> if (test_bit(R10BIO_WriteError,
>

\
 
 \ /
  Last update: 2022-09-14 12:22    [W:0.126 / U:0.628 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site