Date: Mon, 29 Aug 2011 12:27:32 -0500 From: Mark Felder <feld@feld.me> To: freebsd-questions@freebsd.org Subject: Re: Turn off hyperthreading on dual core Atom? Message-ID: <op.v0zj36t634t2sn@tech304> In-Reply-To: <201108291724.LAA18734@lariat.net> References: <201108291724.LAA18734@lariat.net>
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On Mon, 29 Aug 2011 12:24:08 -0500, Brett Glass <brett@lariat.net> 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? In my experience hyperthreading is useful in very few environments. I personally disabled it on my Atom machine which acts as a NAS among other things. I have noticed an improvement in performance and also in responsiveness. YMMV, etc etc etc :-) Regards, Mark
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