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From: Sean Bruno <seanbru@yahoo-inc.com>
To: Ivan Voras <ivoras@freebsd.org>
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Date: Wed, 31 Aug 2011 12:18:42 -0700
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Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject: Re: Large machine test ideas
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On Tue, 2011-08-30 at 17:11 -0700, Ivan Voras wrote:
> On 29.8.2011. 20:15, John Baldwin wrote:
> 
> > However, the SRAT code just ignores the table when it encounters an issue like
> > this, it doesn't hang.  Something else later in the boot must have hung.
> 
> Anyway... that machine can in its maximal configuration be populated 
> with eight 10-core CPUs, i.e. 80 physical / 160 logical, so here's a 
> vote from me to bump the shiny new cpuset infrastructure maximum CPU 
> count to 256 before 9.0.
> 
> http://www.supermicro.com/products/system/5U/5086/SYS-5086B-TRF.cfm

Doesn't that (MAXCPU) seriously impact VM usage, lock contention
etc ... ?

I mean, if we have 2 cpus in a machine, but MAXCPU is set to 256, there
is a bunch of "lost" memory and higher levels of lock contention?

I thought that attilio was taking a stab at enhancing this, but at the
current time anything more than a value of 64 for MAXCPU is kind of a
"caveat emptor" area of FreeBSD.

Sean

P.S.  I say 64 as yahoo has been running 64 cpus with local patches for
a while, so I know that this works fairly well.