Re: sendfile and page usage statistics

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From
David G Lawrence <dg@dglawrence.com>
Date
10 Oct 2007 18:13:01
Subject
Re: sendfile and page usage statistics
Message-ID
20071010181259.GF56714@tnn.dglawrence.com

In reply to

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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.


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