Date: Fri, 28 Feb 2003 14:24:50 -0500 From: Don Bowman <don@sandvine.com> To: 'Steve Grandi' <grandi@noao.edu>, freebsd-stable@freebsd.org Subject: RE: hyperthreading in STABLE: should machdep.cpu_idle_hlt be on? Message-ID: <FE045D4D9F7AED4CBFF1B3B813C8533701B35BD8@mail.sandvine.com>
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> From: Steve Grandi [mailto:grandi@noao.edu] > I've brought up STABLE on a Supermicro X5DPR-8G2+ motherboard > which has > two 2.4GHz Xeons. In the BIOS setup, I disabled > hyperthreading. The BIOS > even prints out a nice message during the POST that hyperthreading is > disabled. > > The BIOS setting notwithstanding, STABLE fires up hyperthreading and > presents me with 4 cpus! > > OK, I will go with the flow: but what is the current wisdom about > machdep.cpu_idle_hlt? Should I set it to 1 to avoid a loss > of performance > and to avoid frying the box? On that motherboard, with our application, we've found that enabling hlt=1 will drop 0.1A of power on the inlet, or about ~12W (going from 2.15A to 2.05A). Our performance increased approx 7% for the same network-centric application, YMMV. We use hyperthreading enabled in the BIOS, and an SMP kernel, it has proven to increase performance in our application. --don To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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