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SubjectRe: [PATCH 1/2] Revert "mm: don't reclaim inodes with many attached pages"
On Wed, Jan 30, 2019 at 12:21:07PM +0000, Chris Mason wrote:
>
>
> On 29 Jan 2019, at 23:17, Dave Chinner wrote:
>
> > From: Dave Chinner <dchinner@redhat.com>
> >
> > This reverts commit a76cf1a474d7dbcd9336b5f5afb0162baa142cf0.
> >
> > This change causes serious changes to page cache and inode cache
> > behaviour and balance, resulting in major performance regressions
> > when combining worklaods such as large file copies and kernel
> > compiles.
> >
> > https://bugzilla.kernel.org/show_bug.cgi?id=202441
>
> I'm a little confused by the latest comment in the bz:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=202441#c24

Which says the first patch that changed the shrinker behaviour is
the underlying cause of the regression.

> Are these reverts sufficient?

I think so.

> Roman beat me to suggesting Rik's followup. We hit a different problem
> in prod with small slabs, and have a lot of instrumentation on Rik's
> code helping.

I think that's just another nasty, expedient hack that doesn't solve
the underlying problem. Solving the underlying problem does not
require changing core reclaim algorithms and upsetting a page
reclaim/shrinker balance that has been stable and worked well for
just about everyone for years.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com

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