On Thu, Apr 27, 2017 at 04:28:49PM +0800, Xiao Ni wrote:
> In new barrier codes, raise_barrier waits if conf->nr_pending[idx] is not zero.
> After all the conditions are true, the resync request can go on be handled. But
> it adds conf->nr_pending[idx] again. The next resync request hit the same bucket
> idx need to wait the resync request which is submitted before. The performance
> of resync/recovery is degraded.
> So we should use a new variable to count sync requests which are in flight.
>
> I did a simple test:
> 1. Without the patch, create a raid1 with two disks. The resync speed:
> Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
> sdb 0.00 0.00 166.00 0.00 10.38 0.00 128.00 0.03 0.20 0.20 0.00 0.19 3.20
> sdc 0.00 0.00 0.00 166.00 0.00 10.38 128.00 0.96 5.77 0.00 5.77 5.75 95.50
> 2. With the patch, the result is:
> sdb 2214.00 0.00 766.00 0.00 185.69 0.00 496.46 2.80 3.66 3.66 0.00 1.03 79.10
> sdc 0.00 2205.00 0.00 769.00 0.00 186.44 496.52 5.25 6.84 0.00 6.84 1.30 100.10
>
> Suggested-by: Shaohua Li <shli@xxxxxxxxxx>
> Signed-off-by: Xiao Ni <xni@xxxxxxxxxx>
applied, thanks!
> ---
> drivers/md/raid1.c | 5 +++--
> drivers/md/raid1.h | 1 +
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index a34f587..ff5ee53 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -869,7 +869,7 @@ static void raise_barrier(struct r1conf *conf, sector_t sector_nr)
> atomic_read(&conf->barrier[idx]) < RESYNC_DEPTH,
> conf->resync_lock);
>
> - atomic_inc(&conf->nr_pending[idx]);
> + atomic_inc(&conf->nr_sync_pending);
> spin_unlock_irq(&conf->resync_lock);
> }
>
> @@ -880,7 +880,7 @@ static void lower_barrier(struct r1conf *conf, sector_t sector_nr)
> BUG_ON(atomic_read(&conf->barrier[idx]) <= 0);
>
> atomic_dec(&conf->barrier[idx]);
> - atomic_dec(&conf->nr_pending[idx]);
> + atomic_dec(&conf->nr_sync_pending);
> wake_up(&conf->wait_barrier);
> }
>
> @@ -1017,6 +1017,7 @@ static int get_unqueued_pending(struct r1conf *conf)
> {
> int idx, ret;
>
> + ret = atomic_read(&conf->nr_sync_pending);
> for (ret = 0, idx = 0; idx < BARRIER_BUCKETS_NR; idx++)
> ret += atomic_read(&conf->nr_pending[idx]) -
> atomic_read(&conf->nr_queued[idx]);
> diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
> index dd22a37..1668f22 100644
> --- a/drivers/md/raid1.h
> +++ b/drivers/md/raid1.h
> @@ -84,6 +84,7 @@ struct r1conf {
> */
> wait_queue_head_t wait_barrier;
> spinlock_t resync_lock;
> + atomic_t nr_sync_pending;
> atomic_t *nr_pending;
> atomic_t *nr_waiting;
> atomic_t *nr_queued;
> --
> 2.7.4
>
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