Date: Mon, 29 Aug 2011 20:55:08 +0100 From: Bruce Cran <bruce@cran.org.uk> To: Brett Glass <brett@lariat.net> Cc: questions@freebsd.org Subject: Re: Turn off hyperthreading on dual core Atom? Message-ID: <4E5BEE9C.7080706@cran.org.uk> In-Reply-To: <201108291724.LAA18734@lariat.net> References: <201108291724.LAA18734@lariat.net>
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On 29/08/2011 18:24, Brett Glass wrote: > With hyperthreading, the FreeBSD scheduler simply acts as if there are > 4 CPUs. Each "CPU" gets clock interrupts (which add overhead), and the > scheduler is naive about the fact that two of the "CPUs" are not > separate chips and could be held up if its mate has a heavy load. I do > not know if the supposed higher utilization of the resources on each > chip (including executing one thread while the CPU waits for data for > another) is worth it. What has your experience been? Actually, the ULE scheduler does know about HyperThreading and the topology of such CPUs. I don't know what it does with the information, but it probably works to optimize cache usage etc. -- Bruce Cran
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