Date: Thu, 17 Apr 2008 17:35:16 -0700 From: "David O'Brien" <obrien@freebsd.org> To: David Malone <dwmalone@maths.tcd.ie> Cc: gnn@freebsd.org, freebsd-current@freebsd.org, Jeff Roberson <jroberson@jroberson.net>, Andrew Gallatin <gallatin@cs.duke.edu> Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <20080418003516.GD11705@dragon.NUXI.org> In-Reply-To: <20080415084602.GA44129@walton.maths.tcd.ie> References: <m2d4oy8n30.wl%gnn@neville-neil.com> <18431.23276.913397.188219@grasshopper.cs.duke.edu> <m27iezwonx.wl%gnn@neville-neil.com> <20080414215057.B959@desktop> <20080415084602.GA44129@walton.maths.tcd.ie>
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On Tue, Apr 15, 2008 at 09:46:02AM +0100, David Malone wrote: > On Mon, Apr 14, 2008 at 09:51:42PM -1000, Jeff Roberson wrote: > > I think we should confirm whether this is the case with earlier opterson. > > I have seen two processors on the same die out of sync. > > This can definitely happen according to this note from AMD, which > someone posted a link to earlier in the thread: > > http://lkml.org/lkml/2005/11/4/173 > > it can happen when you hlt one core, but don't hlt the other on > some processors. Actually that is something slightly different. Even without HLT, RDTSC on the two cores of a dual-core processor can be out of sync. HLT can affect the delta between the two cores. -- -- David (obrien@FreeBSD.org)
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