Date: Mon, 18 Feb 2002 18:35:38 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Terry Lambert <tlambert2@mindspring.com> 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: <20020218182727.C5246-100000@gamplex.bde.org> In-Reply-To: <3C70AB8B.96589869@mindspring.com>
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On Sun, 17 Feb 2002, Terry Lambert wrote:
> 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
argh, usec
> > 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.
This is not long :-), but 440 msec is.
> Up that to 2uS and... = 220ms/sec on time stamps = ~1/4 of
> all available time spent on time stamps.
Bruce
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