Date: Sun, 17 Feb 2002 23:21:47 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Bruce Evans <bde@zeta.org.au> Cc: Matthew Dillon <dillon@apollo.backplane.com>, Poul-Henning Kamp <phk@critter.freebsd.dk>, Julian Elischer <julian@elischer.org>, Alfred Perlstein <bright@mu.org>, arch@FreeBSD.ORG, jhb@FreeBSD.ORG, peter@wemm.org, jake@locore.ca Subject: Re: gettimeofday() and crhold()/crfree() (was Re: gettimeofday()andcopyout().Is copyout() MPSAFE on non-i386 archs? ) Message-ID: <3C70AB8B.96589869@mindspring.com> References: <20020218151249.E4728-100000@gamplex.bde.org>
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Bruce Evans wrote:
> On Sun, 17 Feb 2002, Matthew Dillon wrote:
>
> > Just a note: The gettimeofday() has an overhead of only 2-3 uS in
> > -current. Squid would have to be doing an aweful lot of transactions
>
> And that is only on slow machines and/or under SMP. On my Athlon1600,
> it has an overhead of 0.3-0.4 nsec. I have been benchmarking it for
> many years and recently had to change the benchmark program to use
> clock_gettime(2) instead of gettimeofday() when getttimeofday()'s
> resolution became too small.
.4nsec * 22,000 transactions/sec * 5 timestamps/transaction
= 440us/sec spent on time stamps.
Up that to 2uS and... = 220ms/sec on time stamps = ~1/4 of
all available time spent on time stamps.
[ ... other stuff not really applicable; can discuss why
off list, if necessary ... ]
-- Terry
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