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Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/vm vm_contig.c vm_page.c vm_pageq.c 
 vm_zeroidle.c
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On Mon, 5 Feb 2007, Alan Cox wrote:

> alc         2007-02-05 06:02:55 UTC
>
>  FreeBSD src repository
>
>  Modified files:
>    sys/vm               vm_contig.c vm_page.c vm_pageq.c
>                         vm_zeroidle.c
>  Log:
>  Change the free page queue lock from a spin mutex to a default (blocking)
>  mutex.  With the demise of Alpha support, there is no longer a reason for
>  it to be a spin mutex.

Is there any measurable performance change from this?  In the past, I've 
observed significantly higher cost for acquiring spin mutexes vs. sleep 
mutexes in micro-benchmarking.  The change was most striking on Intel Xeon P4 
hardware with an SMP kernel, and quite a bit less so on other platforms.

Robert N M Watson
Computer Laboratory
University of Cambridge