linux-kernel - Re: [PATCH] mm: Stop kswapd early when nothing's waiting for it to free pages

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Message-ID: <20200219224503.GB5190@sultan-book.localdomain>
Date:   Wed, 19 Feb 2020 14:45:03 -0800
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Stop kswapd early when nothing's waiting for it to
 free pages

On Wed, Feb 19, 2020 at 11:26:53AM -0800, Andrew Morton wrote:
> On Wed, 19 Feb 2020 10:25:22 -0800 Sultan Alsawaf <sultan@...neltoast.com> wrote:
> 
> > Keeping kswapd running when all the failed allocations that invoked it
> > are satisfied incurs a high overhead due to unnecessary page eviction
> > and writeback, as well as spurious VM pressure events to various
> > registered shrinkers. When kswapd doesn't need to work to make an
> > allocation succeed anymore, stop it prematurely to save resources.
> 
> Seems sensible.
> 
> Please fully describe the userspace-visible runtime effects of this
> change?
> 

FWIW, it looks like the refcount API doesn't allow refcounts to be zero, so I'd
have to update this patch to use just plain atomic_t instead. But since there
doesn't seem to be much interest in this, I'll only send an updated patch if
it's desired.

Sultan