From owner-freebsd-questions@FreeBSD.ORG  Fri Mar  2 14:48:41 2007
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Date: Fri, 2 Mar 2007 15:48:34 +0100
From: Divacky Roman <xdivac02@stud.fit.vutbr.cz>
To: Wojciech Puchar <wojtek@tensor.3miasto.net>
Message-ID: <20070302144833.GA87211@stud.fit.vutbr.cz>
References: <45E7F09B.7070005@zedat.fu-berlin.de>
	<20070302104219.B5845@chylonia.3miasto.net>
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Cc: freebsd-performance@freebsd.org,
	"O. Hartmann" <ohartman@zedat.fu-berlin.de>, freebsd-questions@freebsd.org
Subject: Re: (S)ATA performance in FBSD 6.2/7.0
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On Fri, Mar 02, 2007 at 10:43:34AM +0100, Wojciech Puchar wrote:
> >another while the box didn't do anything else than copying. I watched the 
> >copy process via 'systat -vmstat 1' and realized, that the value of 'KB/t' 
> >never go byond 128 (128kb buffer limit?). But more frustrating, I never got
> 
> what's wrong? FreeBSD uses 128k limit by default.
> 
> edit /usr/src/sys/sys/param.h
> 
> and change
> 
> #define MAXPHYS         (128 * 1024)   /* max raw I/O transfer size */
> 
> 
> to say
> 
> #define MAXPHYS         (1024 * 1024)   /* max raw I/O transfer size */

did anyone measure impact on various benchmark of this change? is 128k the
optimal size for "nowadays computers" ? if we can squeeze more performance
out of a typical box by just raising one define it would be great...

roman