linux-kernel - Re: How kernel applies LRU to swap out physical pages?

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Date:	Tue, 11 Nov 2008 18:56:55 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	kosaki.motohiro@...fujitsu.com, Pan ruochen <panruochen@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: How kernel applies LRU to swap out physical pages?

> On Tue, 2008-11-11 at 16:22 +0800, Pan ruochen wrote:
> > Hi All,
> > I'm reading the linux kernel 2.6.14. But can't understand how LRU algorithm
> > is applied to page swapping. what is the 'USED' of LRU referred to? The
> > reference counter which the page is mapped by processes, or the frequency that
> > CPU reads/writes in the page. In common sense, the LRU algorithm will be more
> > optimal for the second case. But it depends on CPU capability.
> > I will be very appreciated if somebody can explain that in details.
> 
> We don't actually use LRU but something like CLOCK.

Yup.

However, VM replace algorithm folks commonly call it to "LRU"
because MACH call so.

IOW, it is historical reason word, shouldn't imazine strict 
"Least Recently Used" algorithm.



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