linux-kernel - Re: [PATCH 0/8] idle page tracking / working set estimation

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Date:	Tue, 27 Sep 2011 22:20:21 +0530
From:	Balbir Singh <bsingharora@...il.com>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <jweiner@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Michael Wolf <mjwolf@...ibm.com>
Subject: Re: [PATCH 0/8] idle page tracking / working set estimation

>>
>> Sorry, I have trouble parsing this sentence, could you elaborate on "when"?
>
> page_referenced() indicates if a page was accessed since the previous
> page_referenced() call.
>
> page_referenced_kstaled() indicates if a page was accessed since the
> previous page_referenced_kstaled() call.
>
> Both of the functions need to clear PTE young bits; however we don't
> want the two functions to interfere with each other. To achieve this,
> we add two page bits to indicate when a young PTE has been observed by
> one of the functions but not by the other.

OK and this gives different page aging schemes for the same page? Is
this to track state changes

PR1 sees: PTE x young as 0
PR2 sees: PTE x as 1, the rest to 0

so PR1 and PR2 will disagree? Should I be looking deeper in the
patches to understand

Balbir
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