On Wed, Aug 7, 2019 at 8:36 AM Jinpu Wang <jinpu.w...@cloud.ionos.com> wrote:
>
> On Wed, Aug 7, 2019 at 1:40 AM NeilBrown <ne...@suse.com> wrote:
> >
> > On Tue, Aug 06 2019, Jinpu Wang wrote:
> >
> > > On Tue, Aug 6, 2019 at 9:54 AM Jinpu Wang <jinpu.w...@cloud.ionos.com>
> > > wrote:
> > >>
> > >> On Tue, Aug 6, 2019 at 1:46 AM NeilBrown <ne...@suse.com> wrote:
> > >> >
> > >> > On Mon, Aug 05 2019, Jinpu Wang wrote:
> > >> >
> > >> > > Hi Neil,
> > >> > >
> > >> > > For the md higher write IO latency problem, I bisected it to these
> > >> > > commits:
> > >> > >
> > >> > > 4ad23a97 MD: use per-cpu counter for writes_pending
> > >> > > 210f7cd percpu-refcount: support synchronous switch to atomic mode.
> > >> > >
> > >> > > Do you maybe have an idea? How can we fix it?
> > >> >
> > >> > Hmmm.... not sure.
> > >> Hi Neil,
> > >>
> > >> Thanks for reply, detailed result in line.
> >
> > Thanks for the extra testing.
> > ...
> > > [ 105.133299] md md0 in_sync is 0, sb_flags 2, recovery 3, external
> > > 0, safemode 0, recovery_cp 524288
> > ...
> >
> > ahh - the resync was still happening. That explains why set_in_sync()
> > is being called so often. If you wait for sync to complete (or create
> > the array with --assume-clean) you should see more normal behaviour.
> I've updated my tests accordingly, thanks for the hint.
> >
> > This patch should fix it. I think we can do better but it would be more
> > complex so no suitable for backports to -stable.
> >
> > Once you confirm it works, I'll send it upstream with a
> > Reported-and-Tested-by from you.
> >
> > Thanks,
> > NeilBrown
>
> Thanks a lot, Neil, my quick test show, yes, it fixed the problem for me.
>
> I will run more tests to be sure, will report back the test result.
Hi Neil,
I've run our regression tests with your patch, everything works fine
as expected.
So Reported-and-Tested-by: Jack Wang <jinpu.w...@cloud.ionos.com>
Thank you for your quick fix.
The patch should go to stable 4.12+
Regards,
Jack Wang
>
> Regards,
> Jack Wang
>
> >
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 24638ccedce4..624cf1ac43dc 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -8900,6 +8900,7 @@ void md_check_recovery(struct mddev *mddev)
> >
> > if (mddev_trylock(mddev)) {
> > int spares = 0;
> > + bool try_set_sync = mddev->safemode != 0;
> >
> > if (!mddev->external && mddev->safemode == 1)
> > mddev->safemode = 0;
> > @@ -8945,7 +8946,7 @@ void md_check_recovery(struct mddev *mddev)
> > }
> > }
> >
> > - if (!mddev->external && !mddev->in_sync) {
> > + if (try_set_sync && !mddev->external && !mddev->in_sync) {
> > spin_lock(&mddev->lock);
> > set_in_sync(mddev);
> > spin_unlock(&mddev->lock);
