Date: Fri, 31 Jan 2003 11:55:43 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Peter Wemm <peter@wemm.org> Cc: Bosko Milekic <bmilekic@unixdaemons.com>, "Daniel C. Sobral" <dcs@tcoip.com.br>, Trish Lynch <trish@bsdunix.net>, freebsd-current@FreeBSD.ORG Subject: Re: Hyperthreading and machdep.cpu_idle_hlt Message-ID: <200301311955.h0VJthKW078662@apollo.backplane.com> References: <20030131194817.335B72A89E@canning.wemm.org>
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:The cache and most of the execution hardware is shared. The execution
:units can run something like 4 instructions per clock. If the "idle"
:logical core is in a spinloop, then it is generating instructions for
:execution, so you are dividing the execution resources between one context
:that is doing real work, and the other context that is burning off the
:"excess" resources. Overall, it is a huge loss. It is absolutely essential
:that logical cpus be halted when they are not doing useful work.
Ah, that makes sense. Are the two logical cpus shared 50-50?
-Matt
:Cheers,
:-Peter
:--
:Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com
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