linux-kernel - Re: [PATCH 2/5] mm: vmscan: kick flushers when we encounter dirty pages on the LRU

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Message-ID: <20170126095745.ueigbrsop5vgmwzj@suse.de>
Date:   Thu, 26 Jan 2017 09:57:45 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 2/5] mm: vmscan: kick flushers when we encounter dirty
 pages on the LRU

On Mon, Jan 23, 2017 at 01:16:38PM -0500, Johannes Weiner wrote:
> Memory pressure can put dirty pages at the end of the LRU without
> anybody running into dirty limits. Don't start writing individual
> pages from kswapd while the flushers might be asleep.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

I don't understand the motivation for checking the wb_reason name. Maybe
it was easier to eyeball while reading ftraces. The comment about the
flusher not doing its job could also be as simple as the writes took
place and clean pages were reclaimed before dirty_expire was reached.
Not impossible if there was a light writer combined with a heavy reader
or a large number of anonymous faults.

Anyway;

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs