Date: Thu, 23 Apr 2009 13:07:58 -0500 From: Josh Ulrich <josh.m.ulrich@gmail.com> To: doc@FreeBSD.org Subject: Possible documentation issue? Message-ID: <8cca69990904231107jf9fe544g9dcc45bda9309b5c@mail.gmail.com>
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Hello, The paragraph below states the default scheduler doesn't optimize for HTT but the default scheduler in the GENERIC kernel in 7.1 is now SCHED_ULE, which includes "CPU topology awareness, including for hyper-threading." (sched_ule(4)) I thought SCHED_ULE differentiates between physical and logical processors. Is that incorrect? From: http://www.freebsd.org/releases/7.1R/hardware.html "FreeBSD will take advantage of HyperThreading (HTT) support on Intel CPUs that support this feature. A kernel with the options SMP feature enabled will automatically detect the additional logical processors. The default FreeBSD scheduler treats the logical processors the same as additional physical processors; in other words, no attempt is made to optimize scheduling decisions given the shared resources between logical processors within the same CPU. Because this naive scheduling can result in suboptimal performance, under certain circumstances it may be useful to disable the logical processors with the the machdep.hlt_logical_cpus sysctl variable. It is also possible to halt any CPU in the idle loop with the machdep.hlt_cpus sysctl variable. The smp(4) manual page has more details." Best Regards, Josh -- http://quantemplation.blogspot.com http://www.fosstrading.com
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