Date: Fri, 3 Dec 1999 10:03:34 +1100 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: arch@freebsd.org Subject: Re: Threads stuff Message-ID: <99Dec3.095608est.40342@border.alcanet.com.au> In-Reply-To: <819.944166174@critter.freebsd.dk> References: <99Dec3.070619est.40333@border.alcanet.com.au> <819.944166174@critter.freebsd.dk>
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On 1999-Dec-03 07:22:54 +1100, Poul-Henning Kamp wrote: >In message <99Dec3.070619est.40333@border.alcanet.com.au>, Peter Jeremy writes: >>On my PII-266, clock_gettime(CLOCK_REALTIME) takes 2.48usec and >>gettimeofday() takes 2.42usec - slightly better. >The time it takes depends on the "timecounter" you are using for >your timekeeping. I will venture to guess that the above numbers >come from a UP machine using the TSC. Ooops, I forgot about that. Yes, this is an UP system using the TSC. AFAIK, I can't swap to the 8254 w/o rebooting. I tried the same thing on a P-133 using the i8254 and got: clock_gettime(CLOCK_REALTIME) 6.92 usec gettimeofday() 5.93 usec (And on a 386SX25 running 2.2.5, I got 115usec). >If the timestamps don't need to be more precise than 1/hz, I suspect that for the purposes in question, it _does_ need to be SMP safe (which writes off the TSC) and will need better than 1/hz precision (though I'm not definite about this). Peter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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