linux-kernel - Re: la la la la ... swappiness

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Message-ID: <4574487F.7040805@nortel.com>
Date:	Mon, 04 Dec 2006 10:10:39 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Aucoin@...ston.RR.com
CC:	"'Kyle Moffett'" <mrmacman_g4@....com>,
	"'Tim Schmielau'" <tim@...sik3.uni-rostock.de>,
	"'Andrew Morton'" <akpm@...l.org>, torvalds@...l.org,
	linux-kernel@...r.kernel.org, clameter@....com
Subject: Re: la la la la ... swappiness

Aucoin wrote:

> The definition of perfectly good here may be up for debate or
> someone can explain it to me. This perfectly good data was
> cached under the tar yet hours after the tar has completed the
> pages are still cached.

If nothing else has asked for that memory since the tar, there is no 
reason to evict the pages from the cache.  The inactive memory is 
basically "free, but still contains the previous data".

If anything asks for memory, those pages will be filled with zeros or 
the new information.  In the meantime, the kernel keeps them in the 
cache in case anyone wants the old information.

It doesn't hurt anything to keep the pages around with the old data in 
them--and it might help.

Chris
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