From owner-freebsd-stable  Fri May  4  9:42:45 2001
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Date: Fri, 04 May 2001 09:42:37 -0700
From: John Merryweather Cooper <jmcoopr@webmail.bmi.net>
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To: Matt Dillon <dillon@earth.backplane.com>
Cc: David Petrou <dpetrou@cs.cmu.edu>, Antoine.Beaupre@ericsson.ca,
	freebsd-stable@FreeBSD.ORG
Subject: Re: Should /sys/i386/conf/GENERIC's SysV shared memory 
 settings+defaults  be re-thought?
References: <20010503221951.G47670@amant.pdl.cs.cmu.edu> <200105041614.f44GEsb25774@earth.backplane.com>
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Matt Dillon wrote:
> 
> :..
> :> while now, on a Pentium 166Mhz with 32M but around 100-150Mb or swap.
> :>
> :> Never had problems with SHM.
> :
> :i've commented about the problems with shm and a heavy enlightenment /
> :gnome load a few weeks ago to stable, but my message was pretty much
> :ignored.  also note that this issue has been brought up in current a
> :year or so ago.
> :
> :my problems went away with:
> :
> :  options  SHMMAXPGS=8192
> :  options  SHMMNI=4096
> :  options  SHMSEG=1024
> :
> :i don't know enough about the internals to know the downside for using
> :these high values, but i'm pretty confident on today's architectures
> :...
> :
> :david
> 
>     In general there is no downside.  Shared memory is swap-backed
>     (though the in-kernel control structures are not).
> 
>     I think it's high time that the system defaults be raised.  I'll do
>     it later today.  You should also be able to raise the defaults
>     using appropriate sysctl's, e.g.:
> 
>     sysctl -a | fgrep kern.ipc
>     sysctl -w kern.ipc.shmmax=33554432
> 
>     And, of course, with kernel conf variables.
> 
>                                                 -Matt

Excellent!  Other than larger swap usage, I haven't seen a downside to
my settings (although I think they're a little on the large end) 
Performance with graphics, particularly with xscreensaver seems much
improved though.

jmc

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