Re: [PATCH 1/2] Revert "mm: don't reclaim inodes with many attached pages"

From: Jan Kara
Date: Thu Feb 07 2019 - 05:27:54 EST

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.

Jan Kara <jack@xxxxxxxx>