Re: [PATCH v2] RAID1: Avoid unnecessary loop to decrease conf->nr_queued in raid1d()

[Shaohua Li <shli@kernel.org>]

On Wed, Nov 16, 2016 at 10:36:32PM +0800, Coly Li wrote:
> 在 2016/11/16 下午10:19, Coly Li 写道:
> [snip]
> > ---
> >  drivers/md/raid1.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> > 
> > Index: linux-raid1/drivers/md/raid1.c
> > ===================================================================
> > --- linux-raid1.orig/drivers/md/raid1.c
> > +++ linux-raid1/drivers/md/raid1.c
> > @@ -2387,17 +2387,17 @@ static void raid1d(struct md_thread *thr
> [snip]
> >  		while (!list_empty(&tmp)) {
> >  			r1_bio = list_first_entry(&tmp, struct r1bio,
> >  						  retry_list);
> >  			list_del(&r1_bio->retry_list);
> > +			spin_lock_irqsave(&conf->device_lock, flags);
> > +			conf->nr_queued--;
> > +			spin_unlock_irqrestore(&conf->device_lock, flags);
> [snip]
> 
> Now I work on another 2 patches for a simpler I/O barrier, and a
> lockless I/O submit on raid1, where conf->nr_queued will be in atomic_t.
> So spin lock expense will not exist any more. Just FYI.

I'd like to hold this patch till you post the simpler I/O barrier, as the patch
itself currently doesn't make the process faster (lock/unlock is much heavier
than the loop).

Thanks,
Shaohua