Date: Fri, 23 Aug 2002 15:11:27 -0700 From: Luigi Rizzo <rizzo@icir.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: current@FreeBSD.ORG Subject: Re: how to compute the skew between TSC in SMP systems ? Message-ID: <20020823151127.A82640@iguana.icir.org> In-Reply-To: <30687.1030139048@critter.freebsd.dk>; from phk@critter.freebsd.dk on Fri, Aug 23, 2002 at 11:44:08PM %2B0200 References: <20020823144256.A82380@iguana.icir.org> <30687.1030139048@critter.freebsd.dk>
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ok, i'll look into the ACPI counter. But you still did not tell me why trying to determine the TSC skew cannot be done reliably ... On Fri, Aug 23, 2002 at 11:44:08PM +0200, Poul-Henning Kamp wrote: > In message <20020823144256.A82380@iguana.icir.org>, Luigi Rizzo writes: > > >I want to find performance problems in the kernel, and to this purpose, > >sometimes i need to timestamp events in the kernel using the > >least-intrusive technique i can use, and hopefully get reasonably ... > Alternatively, consider using "basic-block profiling" (see kernbb(8) and > gcc docs), that will tell you not only how many instructions but also > _which_ instructions are executed. this one does not give timing info at all, and it is probably also on the "terribly intrusive" side of the spectrum... cheers luigi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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