Re: [PATCH] md: Add two chances to update sync/recovery checkpoint

[NeilBrown <neilb@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 2629 bytes --]

On Sat, 15 Sep 2012 16:59:34 +0800 "Jianpeng Ma" <majianpeng@gmail.com> wrote:

> According commit 97e4f42d62badb0f9fbc27c013e89,it has 16 times to update
> checkpoint of sync/recovery in func md_do_sync().
> Because the the size of HDD became larger,the time of sync/recovery may
> taken long times.So the 1/16 of time maybe half hour or more.
> So it should add chance to update checkpoint.
> There are places which can update checkpoint in md_do_sync.
> 1: If call cond_resched and really sched
> 2: If curr_speed is larger than max_sync_spedd
> If above conditions are ok, we can try to update checkpoint.
> 
> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
> ---
>  drivers/md/md.c |   16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 3f6203a..c7993d6 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -7496,7 +7496,14 @@ void md_do_sync(struct mddev *mddev)
>  		 * about not overloading the IO subsystem. (things like an
>  		 * e2fsck being done on the RAID array should execute fast)
>  		 */
> -		cond_resched();
> +		if (cond_resched())
> +			if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> +					mddev->curr_resync_completed != j &&
> +					atomic_read(&mddev->recovery_active) == 0) {
> +				mddev->curr_resync_completed = j;
> +				set_bit(MD_CHANGE_CLEAN, &mddev->flags);
> +				sysfs_notify(&mddev->kobj, NULL, "sync_completed");
> +			}
>  
>  		currspeed = ((unsigned long)(io_sectors-mddev->resync_mark_cnt))/2
>  			/((jiffies-mddev->resync_mark)/HZ +1) +1;
> @@ -7505,6 +7512,13 @@ void md_do_sync(struct mddev *mddev)
>  			if ((currspeed > speed_max(mddev)) ||
>  					!is_mddev_idle(mddev, 0)) {
>  				msleep(500);
> +				if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
> +					mddev->curr_resync_completed != j &&
> +					atomic_read(&mddev->recovery_active) == 0) {
> +					mddev->curr_resync_completed = j;
> +					set_bit(MD_CHANGE_CLEAN, &mddev->flags);
> +					sysfs_notify(&mddev->kobj, NULL, "sync_completed");
> +				}
>  				goto repeat;
>  			}
>  		}

I don't really like this.  These two conditions seems rather arbitrary.
If we want to do a checkpoint more often, we should use some time based test
to do it.

What results do you get with this change?  How often does a checkpoint happen
on a busy system?  How often on an idle system?

A time-based update could be done in user-space.  Just write 'idle' to
'sync_action' and it should do a checkpoint, then immediately restart from
where it left off.

NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]