Date: Mon, 29 Aug 2011 15:15:02 -0600 From: Brett Glass <brett@lariat.net> To: Bruce Cran <bruce@cran.org.uk> Cc: questions@freebsd.org Subject: Re: Turn off hyperthreading on dual core Atom? Message-ID: <201108292115.PAA21491@lariat.net> In-Reply-To: <4E5BEE9C.7080706@cran.org.uk> References: <201108291724.LAA18734@lariat.net> <4E5BEE9C.7080706@cran.org.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
At 01:55 PM 8/29/2011, Bruce Cran wrote: >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. Alas, during a recent kernel build, I used the -j2 command line option in "make" and watched as the scheduler repeatedly assigned two instances of cc (the most CPU-intensive program) to the same core. During that process, I also watched CPU utilization in top(1). The peak was 46% idle, which means that HTT appeared to be making at most a 4% difference. (If the peak were 50% idle, HTT would be doing nothing at all, because top(1) can't tell that there aren't really 4 CPUs.) --Brett Glass
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201108292115.PAA21491>