linux-kernel - Re: [RFC] high system time & lock contention running large mixed workload

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Date:	Thu, 03 Dec 2009 17:14:56 -0500
From:	Larry Woodman <lwoodman@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC] high system time & lock contention running large mixed
	workload

On Tue, 2009-12-01 at 21:20 -0500, Rik van Riel wrote:

> This is reasonable, except for the fact that pages that are moved
> to the inactive list without having the referenced bit cleared are
> guaranteed to be moved back to the active list.
> 
> You'll be better off without that excess list movement, by simply
> moving pages directly back onto the active list if the trylock
> fails.
> 


The attached patch addresses this issue by changing page_check_address()
to return -1 if the spin_trylock() fails and page_referenced_one() to
return 1 in that path so the page gets moved back to the active list.

Also, BTW, check this out: an 8-CPU/16GB system running AIM 7 Compute
has 196491 isolated_anon pages.  This means that ~6140 processes are
somewhere down in try_to_free_pages() since we only isolate 32 pages at
a time, this is out of 9000 processes...


---------------------------------------------------------------------
active_anon:2140361 inactive_anon:453356 isolated_anon:196491
 active_file:3438 inactive_file:1100 isolated_file:0
 unevictable:2802 dirty:153 writeback:0 unstable:0
 free:578920 slab_reclaimable:49214 slab_unreclaimable:93268
 mapped:1105 shmem:0 pagetables:139100 bounce:0

Node 0 Normal free:1647892kB min:12500kB low:15624kB high:18748kB 
active_anon:7835452kB inactive_anon:785764kB active_file:13672kB 
inactive_file:4352kB unevictable:11208kB isolated(anon):785964kB 
isolated(file):0kB present:12410880kB mlocked:11208kB dirty:604kB 
writeback:0kB mapped:4344kB shmem:0kB slab_reclaimable:177792kB 
slab_unreclaimable:368676kB kernel_stack:73256kB pagetables:489972kB 
unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0

202895 total pagecache pages
197629 pages in swap cache
Swap cache stats: add 6954838, delete 6757209, find 1251447/2095005
Free swap  = 65881196kB
Total swap = 67354616kB
3997696 pages RAM
207046 pages reserved
1688629 pages shared
3016248 pages non-shared


View attachment "page_referenced.patch" of type "text/x-patch" (7403 bytes)