From: Wu Fengguang <fengguang.wu@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Theodore Ts'o <tytso@mit.edu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Richard Kennedy <richard@rsk.demon.co.uk>,
Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: linux-mm <linux-mm@kvack.org>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 09/13] writeback: reduce per-bdi dirty threshold ramp up time
Date: Wed, 17 Nov 2010 11:58:30 +0800 [thread overview]
Message-ID: <20101117035906.471176258@intel.com> (raw)
Andrew,
References: <20101117035821.000579293@intel.com>
Content-Disposition: inline; filename=writeback-speedup-per-bdi-threshold-ramp-up.patch
Reduce the dampening for the control system, yielding faster
convergence.
Currently it converges at a snail's pace for slow devices (in order of
minutes). For really fast storage, the convergence speed should be fine.
It makes sense to make it reasonably fast for typical desktops.
After patch, it converges in ~10 seconds for 60MB/s writes and 4GB mem.
So expect ~1s for a fast 600MB/s storage under 4GB mem, or ~4s under
16GB mem, which seems reasonable.
$ while true; do grep BdiDirtyThresh /debug/bdi/8:0/stats; sleep 1; done
BdiDirtyThresh: 0 kB
BdiDirtyThresh: 118748 kB
BdiDirtyThresh: 214280 kB
BdiDirtyThresh: 303868 kB
BdiDirtyThresh: 376528 kB
BdiDirtyThresh: 411180 kB
BdiDirtyThresh: 448636 kB
BdiDirtyThresh: 472260 kB
BdiDirtyThresh: 490924 kB
BdiDirtyThresh: 499596 kB
BdiDirtyThresh: 507068 kB
...
DirtyThresh: 530392 kB
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- linux-next.orig/mm/page-writeback.c 2010-11-15 13:08:16.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-11-15 13:08:28.000000000 +0800
@@ -125,7 +125,7 @@ static int calc_period_shift(void)
else
dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
100;
- return 2 + ilog2(dirty_total - 1);
+ return ilog2(dirty_total - 1) - 1;
}
/*
--
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next reply other threads:[~2010-11-17 3:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-17 3:58 Wu Fengguang [this message]
-- strict thread matches above, loose matches on Subject: below --
2010-11-17 4:27 [PATCH 00/13] IO-less dirty throttling v2 Wu Fengguang
2010-11-17 4:27 ` [PATCH 09/13] writeback: reduce per-bdi dirty threshold ramp up time Wu Fengguang
2010-11-24 11:15 ` Peter Zijlstra
2010-11-24 12:39 ` Wu Fengguang
2010-11-24 12:56 ` Peter Zijlstra
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