Date: Sat, 2 Feb 2008 15:39:12 +0530 From: "Joseph Koshy" <joseph.koshy@gmail.com> To: "Alexander Motin" <mav@freebsd.org> Cc: freebsd-hackers@freebsd.org, freebsd-performance@freebsd.org Subject: Re: Memory allocation performance Message-ID: <84dead720802020209n49c09664p3962fa08f2f9a57c@mail.gmail.com> In-Reply-To: <47A37E14.7050801@FreeBSD.org> References: <47A25412.3010301@FreeBSD.org> <47A25A0D.2080508@elischer.org> <47A2C2A2.5040109@FreeBSD.org> <20080201185435.X88034@fledge.watson.org> <47A37E14.7050801@FreeBSD.org>
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> I have tried it for measuring number of instructions. But I am in doubt > that instructions is a correct counter for performance measurement as > different instructions may have very different execution times depending > on many reasons, like cache misses and current memory traffic. I have > tried to use tsc to count CPU cycles, but got the error: > # pmcstat -n 10000 -S "tsc" -O sample.out > pmcstat: ERROR: Cannot allocate system-mode pmc with specification > "tsc": Operation not supported > What have I missed? You cannot sample with the TSC since the TSC does not interrupt the CPU. For CPU cycles you would probably want to use "p4-global-power-events"; see pmc(3). Regards, Koshy
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