Date: Fri, 09 Nov 2001 17:42:58 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Warner Losh <imp@harmony.village.org> Cc: Sansonetti Laurent <lorenzo@linuxbe.org>, freebsd-hackers@FreeBSD.ORG Subject: Re: Measuring interrupt latency Message-ID: <574.1005324178@critter.freebsd.dk> In-Reply-To: Your message of "Thu, 08 Nov 2001 09:51:36 MST." <200111081651.fA8Gpa744046@harmony.village.org>
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In message <200111081651.fA8Gpa744046@harmony.village.org>, Warner Losh writes: >We found at Timing Solutions when we were trying to measure interrupt >latency that the system time (getnanotime()) gave us measurements with >a larger variance than our expensive scopes that does statistical >gathering. Uhm, you should have used nanotime(), not getnanotime(). getnanotime() returns a timestamp in nanoseconds of the last stored timestamp which may be up to 1/hz seconds old. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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