diff mbox series

[v3,3/5] md/raid10: prevent unnecessary calls to wake_up() in fast path

Message ID 20220916113428.774061-4-yukuai1@huaweicloud.com (mailing list archive)
State Mainlined, archived
Delegated to: Song Liu
Headers show
Series md/raid10: reduce lock contention for io | expand

Commit Message

Yu Kuai Sept. 16, 2022, 11:34 a.m. UTC 
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
in allow_barrier() and raid10_make_request().

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/md/raid10.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Comments

Logan Gunthorpe Sept. 16, 2022, 6:36 p.m. UTC | #1 
On 2022-09-16 05:34, Yu Kuai wrote:
> 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
> in allow_barrier() and raid10_make_request().
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Guoqing Jiang Sept. 18, 2022, 11:38 a.m. UTC | #2 
On 9/16/22 7:34 PM, Yu Kuai wrote:
> 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
> in allow_barrier() and raid10_make_request().
>
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
>   drivers/md/raid10.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index df435d693637..cf452c25e1e5 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;
> @@ -1015,7 +1021,7 @@ 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)
> @@ -1891,7 +1897,7 @@ 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;
>   }
>   

Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>

Thanks,
Guoqing
diff mbox series

Patch

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index df435d693637..cf452c25e1e5 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;
@@ -1015,7 +1021,7 @@  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)
@@ -1891,7 +1897,7 @@  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;
 }