linux-kernel - Re: [PATCH 0/3] mm: support bigger cache workingsets and protect against writes

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Date:	Mon, 4 Apr 2016 20:52:41 +0200
From:	Andres Freund <andres@...razel.de>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 0/3] mm: support bigger cache workingsets and protect
 against writes

Hi Johannes,

On 2016-04-04 13:13:35 -0400, Johannes Weiner wrote:
> this is a follow-up to http://www.spinics.net/lists/linux-mm/msg101739.html
> where Andres reported his database workingset being pushed out by the
> minimum size enforcement of the inactive file list - currently 50% of cache
> - as well as repeatedly written file pages that are never actually read.

Thanks for following up!


> Andres, I tried reproducing your postgres scenario, but I could never get
> the WAL to interfere even with wal_log = hot_standby mode. It's a 8G
> machine, I set shared_buffers = 2GB, ran pgbench -i -s 290, and then -c 32
> -j 32 -M prepared -t 150000. Any input on how to trigger the thrashing you
> observed would be appreciated. But it would be great if you could test these
> patches on your known-problematic setup as well.

I'm unfortunately in the process of moving to the US (as in, I'm packing
boxes), so I can't get back to you just now. I'll try ASAP (early next
week).

Regards,

Andres