Date: Fri, 24 Jan 2003 17:33:44 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: Peter Wemm <peter@wemm.org> Cc: John Baldwin <jhb@FreeBSD.org>, Nate Lawson <nate@root.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, Attila Nagy <bra@fsn.hu> Subject: Re: cvs commit: src/sys/i386/i386 identcpu.c initcpu.c locore.s Message-ID: <20030125013344.GA54764@dhcp01.pn.xcllnt.net> In-Reply-To: <20030125012527.EE5542A89E@canning.wemm.org> References: <XFMail.20030124142224.jhb@FreeBSD.org> <20030125012527.EE5542A89E@canning.wemm.org>
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On Fri, Jan 24, 2003 at 05:25:27PM -0800, Peter Wemm wrote: > John Baldwin wrote: > > > > On 24-Jan-2003 Nate Lawson wrote: > > > On Fri, 24 Jan 2003, Attila Nagy wrote: > > >> Nate Lawson wrote: > > >> > The patch merely enables an Auxiliary Processor on equipment that > > >> > supports HTT. Thus, 4.x still has all its original SMP weaknesses that > > >> > will lead people (eventually) to 5.x including the fact that only one > > >> > process can be active in the kernel at a time. > > >> > > >> And what about performance? I mean those "Auxiliary Processors" are > > >> "weaker" than the real ones, so scheduling CPU intensive processes to them > > >> makes a weird assymmetry. In average for example with a dnetc client > > >> what's better? :) > > >> Running two processes with HT turned off, or running four of them with HT > > >> on? > > > > > > I'm not sure what you mean by "weaker". If you have code that is > > > multi-process and it runs faster on an SMP system than a single CPU > > > system, then it is likely to run faster with HTT than without. Read the > > > Intel pages to find more about HTT. > > > > Maybe. Preliminary buildworld tests on 4.x seem to suggest that HTT > > is slower than UP, but buildworld is just one application. HTT will > > probably be optional on stable. On -current we will eventually use > > ACPI to enumerate CPU's which means that we will respect BIOS settings > > with regards to whether or not HTT is enabled. > > Did you remember to set machdep.cpu_idle_hlt to 1? Failing to set this > will really suck because the logical cores will be spinning like crazy and > stealing execution resources from functional tasks on the other part of the > cpu. What about an increase in cache misses due to a degradation of locality by having a larger, less coherent/dense working set? -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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