Date: Tue, 15 Apr 2008 16:41:22 +0900 From: gnn@freebsd.org To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: current@freebsd.org Subject: Re: TSC Timecounter and multi-core/SMP Message-ID: <m27iezwonx.wl%gnn@neville-neil.com> In-Reply-To: <18431.23276.913397.188219@grasshopper.cs.duke.edu> References: <m2d4oy8n30.wl%gnn@neville-neil.com> <18431.23276.913397.188219@grasshopper.cs.duke.edu>
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At Fri, 11 Apr 2008 08:34:29 -0400 (EDT), Andrew Gallatin wrote: > > > gnn@freebsd.org writes: > > Howdy, > > > > Is the TSC timecounter synchronized across multiple cores and/or > > processors? A quick search seems to indicate it's not but I'd like to > > find a definitive reference on the TSC. > > There is a great comment in the OpenSolaris source code talking about > TSCs and their behavior on SMP systems. See > http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/i86pc/os/timestamp.c > Actually this was a very helpful bit of reading. I also believe that at least per processor there is only 1 TSC, that is, on a 2 or 4 core, all cores share the same TSC. Best, George
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