From owner-cvs-all Fri Jan 31 10:25: 9 2003 Delivered-To: cvs-all@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 76E0F37B401 for ; Fri, 31 Jan 2003 10:25:08 -0800 (PST) Received: from rootlabs.com (root.org [67.118.192.226]) by mx1.FreeBSD.org (Postfix) with SMTP id A1B1043F75 for ; Fri, 31 Jan 2003 10:25:03 -0800 (PST) (envelope-from nate@rootlabs.com) Received: (qmail 96979 invoked by uid 1000); 31 Jan 2003 18:24:58 -0000 Date: Fri, 31 Jan 2003 10:24:58 -0800 (PST) From: Nate Lawson To: John Baldwin Cc: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: RE: cvs commit: src/sys/i386/i386 mp_machdep.c In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Fri, 31 Jan 2003, John Baldwin wrote: > On 30-Jan-2003 Matthew Dillon wrote: > > Ouch. That's rather counter-intuitive since idle_hlt usually > > degrades performance, but I see how it would improve performance on > > an HTT box. > > Well, idle_hlt can only really hurt if you are doing compute bound stuff. > You get at least 128 clock interrupts per second from the RTC that get > IPI'd to all the other CPUs, so no CPU would errantly stay halted for more > than 1/128th of a second with idle_hlt on anyways. As Peter has mentioned, > the idle_hlt thing shows some rather impressive thermal benefits, and I > imagine it can provide power savings of some sort. I would argue that > being fully compute bound is not the common case and that we should probably > default to having it on in general. Why not check CPU utilization and dynamically en/disable HLT? -Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message