On Mon, 11 Jun 2012 17:16:55 +0800 majianpeng <majianpeng@xxxxxxxxx> wrote:
> Add blk_plug in sync_thread will increase the performance of sync.
> Because sync_thread did not blk_plug,so when raid sync, the bio merge
> not well.
>
> Testing environment:
> SATA controller: Intel Corporation 82801JI (ICH10 Family) SATA AHCI
> Controller.
> OS:Linux xxx 3.5.0-rc2+ #340 SMP Tue Jun 12 09:00:25 CST 2012
> x86_64 x86_64 x86_64 GNU/Linux.
> RAID5: four ST31000524NS disk.
>
> Without blk_plug:recovery speed about 63M/Sec;
> Add blk_plug:recovery speed about 120M/Sec.
>
> Using blktrace:
> blktrace -d /dev/sdb -w 60 -o -|blkparse -i -
>
> without blk_plug:
> Total (8,16):
> Reads Queued: 309811, 1239MiB Writes Queued: 0, 0KiB
> Read Dispatches: 283583, 1189MiB Write Dispatches: 0, 0KiB
> Reads Requeued: 0 Writes Requeued: 0
> Reads Completed: 273351, 1149MiB Writes Completed: 0, 0KiB
> Read Merges: 23533, 94132KiB Write Merges: 0, 0KiB
> IO unplugs: 0 Timer unplugs: 0
>
> add blk_plug:
> Total (8,16):
> Reads Queued: 428697, 1714MiB Writes Queued: 0, 0KiB
> Read Dispatches: 3954, 1714MiB Write Dispatches: 0, 0KiB
> Reads Requeued: 0 Writes Requeued: 0
> Reads Completed: 3956, 1715MiB Writes Completed: 0, 0KiB
> Read Merges: 424743, 1698MiB Write Merges: 0, 0KiB
> IO unplugs: 0 Timer unplugs: 3384
>
> The ratio of merge will be markedly increased.
>
> Signed-off-by: majianpeng <majianpeng@xxxxxxxxx>
> ---
> drivers/md/md.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 1c2f904..90bdc37 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -7298,6 +7298,7 @@ void md_do_sync(struct mddev *mddev)
> int skipped = 0;
> struct md_rdev *rdev;
> char *desc;
> + struct blk_plug plug;
>
> /* just incase thread restarts... */
> if (test_bit(MD_RECOVERY_DONE, &mddev->recovery))
> @@ -7446,7 +7447,8 @@ void md_do_sync(struct mddev *mddev)
> mddev->curr_resync = j;
> }
> mddev->curr_resync_completed = j;
> -
> +
> + blk_start_plug(&plug);
> while (j < max_sectors) {
> sector_t sectors;
>
> @@ -7586,6 +7588,7 @@ void md_do_sync(struct mddev *mddev)
> }
> skip:
> set_bit(MD_CHANGE_DEVS, &mddev->flags);
> + blk_finish_plug(&plug);
>
> if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
> /* We completed so min/max setting can be forgotten if used. */
Thanks again.
I've moved the call to "blk_finish_plug" up a bit to just after the
out:
label, as it is possible to "goto skip" before calling blk_start_plug.
Thanks a lot,
NeilBrown
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