Re: [PATCH] ceph: enable async dirops by default

[Ilya Dryomov <idryomov@gmail.com>]

On Wed, Jan 20, 2021 at 1:00 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Wed, 2021-01-20 at 11:46 +0100, Ilya Dryomov wrote:
> > On Tue, Jan 19, 2021 at 4:06 PM Jeff Layton <jlayton@kernel.org> wrote:
> > >
> > > This has been behaving reasonably well in testing, and enabling this
> > > offers significant performance benefits. Enable async dirops by default
> > > in the kclient going forward, and change show_options to add "wsync"
> > > when they are disabled.
> > >
> > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > ---
> > >  fs/ceph/super.c | 4 ++--
> > >  fs/ceph/super.h | 5 +++--
> > >  2 files changed, 5 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> > > index 9b1b7f4cfdd4..884e2ffabfaf 100644
> > > --- a/fs/ceph/super.c
> > > +++ b/fs/ceph/super.c
> > > @@ -577,8 +577,8 @@ static int ceph_show_options(struct seq_file *m, struct dentry *root)
> > >         if (fsopt->flags & CEPH_MOUNT_OPT_CLEANRECOVER)
> > >                 seq_show_option(m, "recover_session", "clean");
> > >
> > > -       if (fsopt->flags & CEPH_MOUNT_OPT_ASYNC_DIROPS)
> > > -               seq_puts(m, ",nowsync");
> > > +       if (!(fsopt->flags & CEPH_MOUNT_OPT_ASYNC_DIROPS))
> > > +               seq_puts(m, ",wsync");
> > >
> > >         if (fsopt->wsize != CEPH_MAX_WRITE_SIZE)
> > >                 seq_printf(m, ",wsize=%u", fsopt->wsize);
> > > diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> > > index 13b02887b085..8ee2745f6257 100644
> > > --- a/fs/ceph/super.h
> > > +++ b/fs/ceph/super.h
> > > @@ -46,8 +46,9 @@
> > >  #define CEPH_MOUNT_OPT_ASYNC_DIROPS    (1<<15) /* allow async directory ops */
> > >
> > >  #define CEPH_MOUNT_OPT_DEFAULT                 \
> > > -       (CEPH_MOUNT_OPT_DCACHE |                \
> > > -        CEPH_MOUNT_OPT_NOCOPYFROM)
> > > +       (CEPH_MOUNT_OPT_DCACHE          |       \
> > > +        CEPH_MOUNT_OPT_NOCOPYFROM      |       \
> > > +        CEPH_MOUNT_OPT_ASYNC_DIROPS)
> > >
> > >  #define ceph_set_mount_opt(fsc, opt) \
> > >         (fsc)->mount_options->flags |= CEPH_MOUNT_OPT_##opt
> > > --
> > > 2.29.2
> > >
> >
> > Hi Jeff,
> >
> > Is it being tested by teuthology?   I see commit 4181742a3ba8 ("qa:
> > allow arbitrary mount options on kclient mounts"), but nothing beyond
> > that.  I think "nowsync" needs to be turned on and get at least some
> > nightly coverage before the default is flipped.
> >
> > Thanks,
> >
> >                 Ilya
>
> Good point. I had thought Patrick had added a qa variant that turned
> that on, but I don't think that ever got merged. We definitely need that
> enabled in QA before we make this the default.
>
> The catch is that we probably don't _always_ want nowsync enabled, so is
> there some way to randomize this? Or do we need some sort of yaml file
> that turns this on by request? What should we be aiming to do for this?

It can be randomized, you can choose to run a particular set of
jobs with both wsync and nowsync and the rest only with wsync or the
other way around, etc.  Completely up to you, depending on the sort
of coverage you want to get (weighted by the number of jobs added to
the suite).

Thanks,

                Ilya