Am Donnerstag, 7. Februar 2019, 11:27:50 schrieb Jan Kara:
> On Fri 01-02-19 09:19:04, Dave Chinner wrote:
> > Maybe for memcgs, but that's exactly the oppose of what we want to
> > do for global caches (e.g. filesystem metadata caches). We need to
> > make sure that a single, heavily pressured cache doesn't evict small
> > caches that lower pressure but are equally important for
> > performance.
> >
> > e.g. I've noticed recently a significant increase in RMW cycles in
> > XFS inode cache writeback during various benchmarks. It hasn't
> > affected performance because the machine has IO and CPU to burn, but
> > on slower machines and storage, it will have a major impact.
>
> Just as a data point, our performance testing infrastructure has bisected
> down to the commits discussed in this thread as the cause of about 40%
> regression in XFS file delete performance in bonnie++ benchmark.
We also bisected our big IO-performance problem of an imap-server (starting
with 4.19.3) down to
mm: don't reclaim inodes with many attached pages
commit a76cf1a474d7dbcd9336b5f5afb0162baa142cf0 upstream.
On other servers the filesystems sometimes seems to hang for 10 seconds and
more.
We also see a performance regression compared to 4.14 even with this patch
reverted, but much less dramatic.
Now I saw this thread and I'll try to revert
172b06c32b949759fe6313abec514bc4f15014f4
and see if this helps.
Regards,
--
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
