From: "H. Peter Anvin" <hpa@zytor.com>
To: Jamie Lokier <lk@tantalophile.demon.co.uk>
Cc: linux-kernel@vger.kernel.org, Alan Cox <alan@lxorguk.ukuu.org.uk>,
Terje Eggestad <terje.eggestad@scali.com>,
Ben Greear <greearb@candelatech.com>,
Davide Libenzi <davidel@xmailserver.org>,
george anzinger <george@mvista.com>
Subject: Re: gettimeofday() system call timing curiosity
Date: Fri, 08 Mar 2002 10:50:53 -0800 [thread overview]
Message-ID: <3C89080D.8060503@zytor.com> (raw)
In-Reply-To: <E16iz57-0002SW-00@the-village.bc.nu> <1015515815.4373.61.camel@pc-16.office.scali.no> <a68bo4$b18$1@cesium.transmeta.com> <20020308013222.B14779@kushida.apsleyroad.org> <3C88157E.5010106@zytor.com> <20020308015701.C14779@kushida.apsleyroad.org> <20020308183049.A18247@kushida.apsleyroad.org>
Jamie Lokier wrote:
>
> On my laptop, the median of rdtsc+gettimeofday+rdtsc times is 470 cycles
> for most runs of 1000, but is occasionally 453 cycles.
>
What that indicates to me is that 1000 is way too small of a sample.
You're only talking a difference of 17,000 cycles, which could --
especially with cache effects -- easily be the time spent in an
interrupt handler.
-hpa
next prev parent reply other threads:[~2002-03-08 18:51 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-06 3:41 a faster way to gettimeofday? Ben Greear
2002-03-06 3:58 ` Davide Libenzi
2002-03-06 4:20 ` Ben Greear
2002-03-06 4:31 ` Davide Libenzi
2002-03-06 4:34 ` Davide Libenzi
2002-03-07 14:14 ` a faster way to gettimeofday? rdtsc strangeness Terje Eggestad
2002-03-07 14:41 ` Alan Cox
2002-03-07 15:43 ` Terje Eggestad
2002-03-07 16:17 ` Alan Cox
2002-03-07 18:32 ` H. Peter Anvin
2002-03-08 1:32 ` Jamie Lokier
2002-03-08 1:35 ` H. Peter Anvin
2002-03-08 1:57 ` Jamie Lokier
2002-03-08 18:30 ` gettimeofday() system call timing curiosity Jamie Lokier
2002-03-08 18:50 ` H. Peter Anvin [this message]
2002-03-08 20:16 ` Jamie Lokier
2002-03-08 20:30 ` Davide Libenzi
2002-03-08 18:54 ` Richard B. Johnson
2002-03-08 19:06 ` johan.adolfsson
2002-03-08 19:16 ` H. Peter Anvin
2002-03-08 19:45 ` Richard B. Johnson
2002-03-08 20:29 ` johan.adolfsson
2002-03-08 20:43 ` Alan Cox
2002-03-09 3:03 ` pjd
2002-03-09 18:51 ` Alan Cox
2002-03-09 3:15 ` Kelsey Hudson
2002-03-08 19:19 ` Alan Cox
2002-03-08 20:40 ` george anzinger
2002-03-06 20:45 ` a faster way to gettimeofday? dean gaudet
2002-03-06 21:31 ` Chris Ball
2002-03-06 22:25 ` george anzinger
2002-03-07 0:04 ` vsyscalls Mark Mielke
2002-03-06 16:16 ` a faster way to gettimeofday? Chris Friesen
2002-03-06 16:54 ` Richard B. Johnson
2002-03-11 22:47 ` OBATA Noboru
2002-03-12 13:06 ` Jamie Lokier
2002-03-12 15:12 ` OBATA Noboru
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