Date: Sat, 29 Oct 2005 09:38:21 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Robert Watson <rwatson@FreeBSD.org> Cc: Pertti Kosunen <pertti.kosunen@pp.nic.fi>, David Xu <davidxu@freebsd.org>, "Yuriy N. Shkandybin" <jura@networks.ru>, current@freebsd.org Subject: Re: Timers and timing, was: MySQL Performance 6.0rc1 Message-ID: <37685.1130571501@critter.freebsd.dk> In-Reply-To: Your message of "Sat, 29 Oct 2005 01:01:59 BST." <20051029005719.I20147@fledge.watson.org>
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In message <20051029005719.I20147@fledge.watson.org>, Robert Watson writes: >It strikes me that replacing time(3) with something that retrieves >CLOCK_SECOND shouldn't harm time(3) semantics. It will mean that time(3) is can do minor (~1/hz) timetravel relative to the other calls: clock_gettime() time(3) 123.999999123 123 124.000000234 123 124.000020300 123 124.000983092 123 (hardclock happens) 124.001020934 124 If we can live with this, there is no problem. >Likewise, keeping >CLOCK_REALTIME as is is likely OK -- if an application requests it using >clock_gettime(), then it is presumably looking for high accuracy. Yes, I think clock_gettime(CLOCK_REALTIME) should remain unchanged. >It's >gettimeofday() that's the troubling one -- it's widely used to query the >time in applications, and its API suggests microsecond resolution. And we don't really have a cheap way to do that... -- 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.
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