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.
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
