On Sun, Jan 24, 2021 at 09:54:54AM +0000, Christoph Hellwig wrote:
> > log->l_ioend_workqueue = alloc_workqueue("xfs-log/%s",
> > - WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_HIGHPRI, 0,
> > - mp->m_super->s_id);
> > + WQ_SYSFS | WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_HIGHPRI,
> > + 0, mp->m_super->s_id);
>
> This is just used for log I/O completions which are effectlively single
> thread. I don't see any reason to adjust the parameters here.
>
> > if (!log->l_ioend_workqueue)
> > goto out_free_iclog;
> >
> > diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
> > index a06661dac5be..b6dab34e361d 100644
> > --- a/fs/xfs/xfs_mru_cache.c
> > +++ b/fs/xfs/xfs_mru_cache.c
> > @@ -294,7 +294,7 @@ int
> > xfs_mru_cache_init(void)
> > {
> > xfs_mru_reap_wq = alloc_workqueue("xfs_mru_cache",
> > - WQ_MEM_RECLAIM|WQ_FREEZABLE, 1);
> > + WQ_SYSFS | WQ_MEM_RECLAIM | WQ_FREEZABLE, 1);
> > if (!xfs_mru_reap_wq)
> > return -ENOMEM;
>
> This one also hasn't ever been something we tune, so I don't think there
> is a good case for enabling WQ_SYSFS.
Yeah, the only ones I want to push for (and hence document) are
quotacheck, background blockgc, and (in 5.13) background inode
inactivation.
> I've stopped here. I think we should have a good use case for making
> workqueues show up in sysfs based on that we:
>
> a) have resons to adjust them ever
> b) actually having them easily discoverable and documented for adminds
> to tune
TBH I think the only workqueues we really ought to expose publicly are
the unbound ones, since they represent kernel threads that can log
transactions, and hence are known to have a performance impact that
sysadmins could tune reasonably.
Dave suggests exposing them all on a debug kernel, of course. :)
--D
