From: Andrea Arcangeli <aarcange@redhat.com>
To: Shaohua Li <shaohua.li@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
"Chen, Tim C" <tim.c.chen@intel.com>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: too big min_free_kbytes
Date: Mon, 24 Jan 2011 16:00:34 +0100 [thread overview]
Message-ID: <20110124150033.GB9506@random.random> (raw)
In-Reply-To: <1295841406.1949.953.camel@sli10-conroe>
eOn Mon, Jan 24, 2011 at 11:56:46AM +0800, Shaohua Li wrote:
> Hi,
> With transparent huge page, min_free_kbytes is set too big.
> Before:
> Node 0, zone DMA32
> pages free 1812
> min 1424
> low 1780
> high 2136
> scanned 0
> spanned 519168
> present 511496
>
> After:
> Node 0, zone DMA32
> pages free 482708
> min 11178
> low 13972
> high 16767
> scanned 0
> spanned 519168
> present 511496
> This caused different performance problems in our test. I wonder why we
> set the value so big.
It's to enable Mel's anti-frag that keeps pageblocks with movable and
unmovable stuff separated, same as "hugeadm
--set-recommended-min_free_kbytes".
Now that I checked, I'm seeing quite too much free memory with only 4G
of ram... You can see the difference with a "cp /dev/sda /dev/null" in
background interleaving these two commands:
echo always >/sys/kernel/mm/transparent_hugepage/enabled
echo 1000 > /proc/sys/vm/min_free_kbytes
The setting of min_free_kbytes to 67584 leads to 716MB of memory
free. Setting to 1000 leads to 20MB free. I'm afraid losing 716MB on a
4G system is way excessive regardless of THP... can't we just have a
version of anti-frag that reserves a lot fewers pageblocks? Anti-frag
is quite important to avoid slab to fragment everything. I don't think
we can leave it like this.
For now you can workaround with the above echo 1000 > ...
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next prev parent reply other threads:[~2011-01-24 15:01 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-24 3:56 too big min_free_kbytes Shaohua Li
2011-01-24 15:00 ` Andrea Arcangeli [this message]
2011-01-25 14:35 ` Mel Gorman
2011-01-26 14:17 ` Mel Gorman
2011-01-26 15:23 ` Mel Gorman
2011-01-26 15:42 ` Andrea Arcangeli
2011-01-26 16:36 ` Mel Gorman
2011-01-26 17:42 ` Mel Gorman
2011-01-27 13:40 ` Mel Gorman
2011-01-27 15:27 ` Andrea Arcangeli
2011-01-27 16:03 ` Mel Gorman
2011-01-27 18:52 ` Andrea Arcangeli
2011-01-27 20:33 ` Rik van Riel
2011-01-27 21:31 ` Mel Gorman
2011-01-27 23:18 ` Rik van Riel
2011-01-28 10:35 ` Mel Gorman
2011-01-28 16:28 ` Andrea Arcangeli
2011-01-28 16:46 ` Mel Gorman
2011-01-28 17:16 ` Rik van Riel
2011-01-28 17:46 ` Andrea Arcangeli
2011-01-28 18:03 ` Rik van Riel
2011-01-28 18:24 ` Andrea Arcangeli
2011-01-28 19:34 ` Rik van Riel
2011-01-28 19:45 ` Andrea Arcangeli
2011-01-28 20:55 ` Rik van Riel
2011-01-29 19:45 ` Andrea Arcangeli
2011-01-28 17:34 ` Andrea Arcangeli
2011-01-28 17:10 ` Rik van Riel
2011-02-03 2:58 ` Andrea Arcangeli
2011-02-03 13:15 ` Mel Gorman
2011-02-03 18:59 ` Andrea Arcangeli
2011-02-03 14:36 ` Rik van Riel
2011-02-03 19:11 ` Andrea Arcangeli
2011-02-12 1:28 ` Simon Kirby
2011-02-14 2:25 ` Shaohua Li
2011-02-22 14:25 ` Mel Gorman
2011-02-22 14:42 ` Andrea Arcangeli
2011-02-22 14:50 ` Mel Gorman
2011-02-22 14:54 ` Andrea Arcangeli
2011-02-22 16:04 ` Mel Gorman
2011-02-22 16:40 ` Rik van Riel
2011-02-23 5:29 ` Shaohua Li
2011-02-23 14:45 ` Andrea Arcangeli
2011-02-24 8:08 ` Shaohua Li
2011-02-24 9:52 ` Mel Gorman
2011-02-24 9:57 ` Mel Gorman
2011-02-24 14:27 ` Andrea Arcangeli
2011-02-24 14:04 ` Andrea Arcangeli
2011-02-25 0:51 ` Shaohua Li
2011-02-25 12:13 ` Mel Gorman
2011-02-12 9:48 ` alex shi
2011-02-22 14:24 ` Mel Gorman
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