Date: Wed, 10 Oct 2007 09:57:48 +0400 From: Igor Sysoev <is@rambler-co.ru> To: freebsd-current@freebsd.org Subject: Re: sendfile and page usage statistics Message-ID: <20071010055748.GA18931@rambler-co.ru> In-Reply-To: <20071009125001.GC5758@rambler-co.ru> References: <20071009125001.GC5758@rambler-co.ru>
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On Tue, Oct 09, 2007 at 04:50:01PM +0400, Igor Sysoev wrote:
> As I understand if sendfile() with hardware TX chsum or TSO are used,
> then CPU does not touch file pages at all. So pagedaemon never set
> PG_REFERENCED to vnode object pages while scanning them.
> Does VM set PG_REFERENCED by another way ? Otherwise, often used files
> that accessed by sendfile() only have small chances to be cached by VM.
I have looked kern_sendfile() in CURRENT and it seems to me that
PG_REFERENCED is never set when sendfile() gets cached vm_page.
I have looked the code path:
vm_page_grab()
vm_page_lookup()
vm_page_wire()
sf_buf_alloc() on i386 and amd64
and have not seen PG_REFERENCED.
--
Igor Sysoev
http://sysoev.ru/en/
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