From owner-freebsd-current  Wed Mar  7  6:38:19 2001
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To: Bruce Evans <bde@zeta.org.au>
Cc: Maxim Sobolev <sobomax@FreeBSD.ORG>, dougb@FreeBSD.ORG,
	current@FreeBSD.ORG
Subject: Re: harvest_interrupt=YES slows down machine 
References: <Pine.BSF.4.21.0103080020001.2722-100000@besplex.bde.org> 
In-Reply-To: <Pine.BSF.4.21.0103080020001.2722-100000@besplex.bde.org> ; from Bruce Evans <bde@zeta.org.au>  "Thu, 08 Mar 2001 00:42:39 +1100."
Date: Wed, 07 Mar 2001 16:38:40 +0200
From: Mark Murray <mark@grondar.za>
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> Just do something that causes a lot of interrupts that go through the
> random harvester.  E.g.:
> 
>     dd if=/dev/ad0 of=/dev/null
> 
> causes 7750 interrupts/sec here (on a Celeron 366 overclocked to
> 522).  The random task takes 100% of the available cpu cycles.  This
> slows down cpu-bound processes by a factor of about 3.5.  With a block
> size of 64k instead of the default of 512, this causes only 300
> interrupts/sec.  The random task takes a measly 27% of the cpu to
> process these.  It can apparently only handle about 10 interrupts/second
> with a reasonable overhead (1%).

OK. Try tweaking the "Computational intensity factor" ;-) by dropping
the kern.random.yarrow.bins:

# sysctl -w kern.random.yarrow.bins=2

And let me know how well that works.

M
-- 
Mark Murray
Warning: this .sig is umop ap!sdn

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