From: Wu Fengguang <fengguang.wu@intel.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>, XFS <xfs@oss.sgi.com>,
Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
Johannes Weiner <jweiner@redhat.com>, Jan Kara <jack@suse.cz>,
Rik van Riel <riel@redhat.com>,
Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback
Date: Tue, 16 Aug 2011 22:06:52 +0800 [thread overview]
Message-ID: <20110816140652.GC13391@localhost> (raw)
In-Reply-To: <1312973240-32576-7-git-send-email-mgorman@suse.de>
Mel,
I tend to agree with the whole patchset except for this one.
The worry comes from the fact that there are always the very possible
unevenly distribution of dirty pages throughout the LRU lists. This
patch works on local information and may unnecessarily throttle page
reclaim when running into small spans of dirty pages.
One possible scheme of global throttling is to first tag the skipped
page with PG_reclaim (as you already do). And to throttle page reclaim
only when running into pages with both PG_dirty and PG_reclaim set,
which means we have cycled through the _whole_ LRU list (which is the
global and adaptive feedback we want) and run into that dirty page for
the second time.
One test scheme would be to read/write a sparse file fast with some
average 5:1 or 10:1 or whatever read:write ratio. This can effectively
spread dirty pages all over the LRU list. It's a practical test since
it mimics the typical file server workload with concurrent downloads
and uploads.
Thanks,
Fengguang
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next prev parent reply other threads:[~2011-08-16 14:06 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-10 10:47 [PATCH 0/7] Reduce filesystem writeback from page reclaim v3 Mel Gorman
2011-08-10 10:47 ` [PATCH 1/7] mm: vmscan: Do not writeback filesystem pages in direct reclaim Mel Gorman
2011-08-10 12:40 ` Johannes Weiner
2011-08-11 9:03 ` KAMEZAWA Hiroyuki
2011-08-11 15:57 ` Rik van Riel
2011-08-10 10:47 ` [PATCH 2/7] mm: vmscan: Remove dead code related to lumpy reclaim waiting on pages under writeback Mel Gorman
2011-08-10 12:41 ` Johannes Weiner
2011-08-10 23:19 ` Minchan Kim
2011-08-11 9:05 ` KAMEZAWA Hiroyuki
2011-08-11 16:52 ` Rik van Riel
2011-08-10 10:47 ` [PATCH 3/7] xfs: Warn if direct reclaim tries to writeback pages Mel Gorman
2011-08-11 16:53 ` Rik van Riel
2011-08-10 10:47 ` [PATCH 4/7] ext4: " Mel Gorman
2011-08-11 17:07 ` Rik van Riel
2011-08-10 10:47 ` [PATCH 5/7] mm: vmscan: Do not writeback filesystem pages in kswapd except in high priority Mel Gorman
2011-08-10 12:44 ` Johannes Weiner
2011-08-11 9:10 ` KAMEZAWA Hiroyuki
2011-08-11 20:25 ` Mel Gorman
2011-08-17 1:06 ` KAMEZAWA Hiroyuki
2011-08-11 18:18 ` Rik van Riel
2011-08-11 20:38 ` Mel Gorman
2011-08-10 10:47 ` [PATCH 6/7] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback Mel Gorman
2011-08-11 9:18 ` KAMEZAWA Hiroyuki
2011-08-12 2:47 ` Rik van Riel
2011-08-16 14:06 ` Wu Fengguang [this message]
2011-08-16 15:02 ` Mel Gorman
2011-08-18 14:02 ` Wu Fengguang
2011-08-18 23:54 ` Andrew Morton
2011-08-30 13:49 ` Mel Gorman
2011-08-31 9:53 ` Mel Gorman
2011-08-10 10:47 ` [PATCH 7/7] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes Mel Gorman
2011-08-10 23:22 ` Minchan Kim
2011-08-11 9:19 ` KAMEZAWA Hiroyuki
2011-08-12 15:27 ` Rik van Riel
2011-08-10 11:00 ` [PATCH 0/7] Reduce filesystem writeback from page reclaim v3 Christoph Hellwig
2011-08-10 11:15 ` Mel Gorman
2011-08-11 23:45 ` Christoph Hellwig
2011-08-18 23:54 ` Andrew Morton
2011-08-20 19:33 ` Mel Gorman
2011-08-30 13:19 ` Mel Gorman
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