From: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
To: Pavel Machek <pavel@elf.ucw.cz>, Andrea Arcangeli <andrea@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
Mikael Pettersson <mikpe@csd.uu.se>,
john stultz <johnstul@us.ibm.com>,
Marcelo Tosatti <marcelo@conectiva.com.br>,
lkml <linux-kernel@vger.kernel.org>,
Leah Cunningham <leahc@us.ibm.com>,
wilhelm.nuesser@sap.com, paramjit@us.ibm.com, msw@redhat.com
Subject: Re: [PATCH] tsc-disable_B9
Date: Mon, 26 Aug 2002 11:45:36 -0700 [thread overview]
Message-ID: <159220000.1030387536@flay> (raw)
In-Reply-To: <20020826161031.GA479@elf.ucw.cz>
>> And following your argument that these apps have been silenty broken
>> since 1999, if there's no broken app out there, nobody will ever get the
>> instruction fault. If there's any app broken out there we probably like
>
> No. rdtsc is still usefull if you are clever and statistically filter
> out. Also rdtsc provides you number of cycles, so if you want to know
> how many cycles mov %eax,%ebx takes, you can do that even on
> speedstep. Anything that correlates rdtsc to real time is broken, however.
It's not correlating it to real time that's the problem. It's getting resceduled
inbetween calls that hurts. Take your example.
rdtsc
mov %eax,%ebx
<- get rescheduled here
rdtsc
Broken. May even take negative "time".
M.
next prev parent reply other threads:[~2002-08-26 18:47 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-08 1:53 [PATCH] tsc-disable_B9 john stultz
2002-08-08 2:15 ` [PATCH] cyclone-timer_A9 john stultz
2002-08-08 13:18 ` Alan Cox
2002-08-09 2:03 ` john stultz
2002-08-08 13:17 ` [PATCH] tsc-disable_B9 Alan Cox
2002-08-09 2:30 ` john stultz
2002-08-09 9:17 ` Alan Cox
2002-08-09 17:46 ` john stultz
2002-08-09 18:49 ` george anzinger
2002-08-09 20:58 ` john stultz
2002-08-13 1:23 ` James Cleverdon
2002-08-11 20:16 ` Alan Cox
2002-08-15 16:56 ` Andrea Arcangeli
2002-08-16 11:15 ` Alan Cox
2002-08-16 13:19 ` Mikael Pettersson
2002-08-21 13:12 ` Andrea Arcangeli
2002-08-21 14:10 ` Alan Cox
2002-08-21 14:33 ` Andrea Arcangeli
2002-08-21 15:01 ` Alan Cox
2002-08-21 16:13 ` Andrea Arcangeli
2002-08-21 16:25 ` Alan Cox
2002-08-21 17:17 ` Andrea Arcangeli
2002-08-21 17:34 ` Alan Cox
2002-08-26 16:10 ` Pavel Machek
2002-08-26 18:45 ` Martin J. Bligh [this message]
2002-08-26 19:00 ` Pavel Machek
2002-08-26 19:05 ` Alan Cox
2002-08-26 20:19 ` Martin J. Bligh
2002-08-26 19:18 ` Richard B. Johnson
2002-08-26 19:42 ` Pavel Machek
2002-08-26 20:23 ` Alan Cox
2002-08-26 22:49 ` Andrea Arcangeli
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