linux-kernel - Re: [PATCH 00 of 66] Transparent Hugepage Support #32

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Date:	Wed, 3 Nov 2010 23:10:47 -0400 (EDT)
From:	caiqian@...hat.com
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>, Adam Litke <agl@...ibm.com>,
	Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>, bpicco@...hat.com,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Chris Mason <chris.mason@...cle.com>,
	Borislav Petkov <bp@...en8.de>, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00 of 66] Transparent Hugepage Support #32

There were some changes of behaviours with THP and KSM statistics demonstrated by this program, http://people.redhat.com/qcai/ksm01.c. 

There are 3 programs (A, B ,C) to allocate 128M memory each using KSM.
A has memory content = 'c'.
B has memory content = 'a'.
C has memory content = 'a'.
Then without THP,
pages_shared = 2
pages_sharing = 98285
pages_sharing = 98292
pages_unshared = 0
pages_volatile = 17
pages_to_scan = 98304
sleep_millisecs = 0
with THP,
pages_shared is 2.
pages_sharing is 18422.
pages_unshared is 0.
pages_volatile is 8.

Later,
A has memory content = 'c'
B has memory content = 'b'
C has memory content = 'a'.
Then without THP,
pages_shared = 3
pages_sharing = 98296
pages_unshared = 0
pages_volatile = 5
with THP,
pages_shared = 3
pages_sharing = 16358
pages_unshared = 0
pages_volatile = 23

Later,
A has memory content = 'd'
B has memory content = 'd'
C has memory content = 'd'
Then without THP,
pages_shared = 1
pages_sharing = 98274
pages_unshared = 0
pages_volatile = 29
with THP,
pages_shared = 1
pages_sharing = 8668
pages_unshared = 0
pages_volatile = 35

Finally,
A changes one page to 'e'
Then without THP,
pages_shared = 1
pages_sharing = 98274
pages_unshared = 1
pages_volatile = 28
with THP,
pages_shared = 1
pages_sharing = 8163
pages_unshared = 1
pages_volatile = 27

Are those differences for pages_sharing between with and without THP are expected?

CAI Qian
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