On Mon, 02 Jul 2012 09:08:41 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote:
> Currently the sequential read detection is global wide. It's natural to make it
> per disk based, which can improve the detection for concurrent multiple
> sequential reads. And next patch will make SSD read balance not use distance
> based algorithm, where this change help detect truly sequential read for SSD.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> drivers/md/raid1.c | 29 ++++++-----------------------
> drivers/md/raid1.h | 11 +++++------
> 2 files changed, 11 insertions(+), 29 deletions(-)
>
> Index: linux/drivers/md/raid1.c
> ===================================================================
> --- linux.orig/drivers/md/raid1.c 2012-06-28 10:44:47.550666575 +0800
> +++ linux/drivers/md/raid1.c 2012-06-28 12:01:03.513137377 +0800
> @@ -483,7 +483,6 @@ static int read_balance(struct r1conf *c
> const sector_t this_sector = r1_bio->sector;
> int sectors;
> int best_good_sectors;
> - int start_disk;
> int best_disk;
> int i;
> sector_t best_dist;
> @@ -503,20 +502,17 @@ static int read_balance(struct r1conf *c
> best_good_sectors = 0;
>
> if (conf->mddev->recovery_cp < MaxSector &&
> - (this_sector + sectors >= conf->next_resync)) {
> + (this_sector + sectors >= conf->next_resync))
> choose_first = 1;
> - start_disk = 0;
> - } else {
> + else
> choose_first = 0;
> - start_disk = conf->last_used;
> - }
>
> for (i = 0 ; i < conf->raid_disks * 2 ; i++) {
> sector_t dist;
> sector_t first_bad;
> int bad_sectors;
>
> - int disk = start_disk + i;
> + int disk = i;
> if (disk >= conf->raid_disks)
> disk -= conf->raid_disks;
One last little change please. Could you make that loop:
for (disk = 0; disk < conf->raid_disks * 2; disk++)
and remote the 'if' statement that wraps 'disk' back to zero
when it gets too big (which is buggy and has been fixed in my for-next).
With that change I'll take the patch.
Thanks,
NeilBrown
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