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Date: Wed, 10 Oct 2007 11:12:59 -0700
From: David G Lawrence <dg@dglawrence.com>
To: Igor Sysoev <is@rambler-co.ru>
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Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-current@freebsd.org,
	Antony Mawer <fbsd-current@mawer.org>
Subject: Re: sendfile and page usage statistics
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> The read() from file certainly updates vnode pages' PG_A/PG_REFERENCED,
> because coping to userland is made by CPU. I think write() does the same.

   No, it does not. The kernel virtual mappings involved in that copy
are "special"; page bits (PG_A, PG_M, etc) from those mapping are not
preserved from the PTEs (at least not on x86).
 
-DG

David G. Lawrence
President
Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500
The FreeBSD Project - http://www.freebsd.org
Pave the road of life with opportunities.