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

[Dave Chinner <david@fromorbit.com>]

On Thu, Feb 07, 2019 at 09:37:27PM -0800, Andrew Morton wrote:
> On Thu, 7 Feb 2019 11:27:50 +0100 Jan Kara <jack@suse.cz> wrote:
> 
> > 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.
> > 
> 
> Has anyone done significant testing with Rik's maybe-fix?

Apart from pointing out all the bugs and incorrect algorithmic
assumptions it makes, no.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com