Date: Wed, 7 Mar 2001 09:32:50 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Mark Murray <mark@grondar.za> Cc: Bruce Evans <bde@zeta.org.au>, Maxim Sobolev <sobomax@FreeBSD.ORG>, dougb@FreeBSD.ORG, current@FreeBSD.ORG Subject: Re: harvest_interrupt=YES slows down machine Message-ID: <200103071732.f27HWou70340@earth.backplane.com> References: <Pine.BSF.4.21.0103080020001.2722-100000@besplex.bde.org> <200103071437.f27EbmR59707@gratis.grondar.za>
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:> 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
I think it would be a much better idea to cap the number of interrupts
per second the reseeder accepts. e.g. have a sysctl to set the
max and default it to something reasonable, like 200. The seeder would
thus only run 200 times a second even if A person were getting
7750 interrupts/sec. Frankly, once we have a good random seed it would
only take about 10 interrupts a second to keep the random number
generator in good shape, and possibly even less. Overkill is not
necessary.
-Matt
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