From: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Pavel Machek <pavel@elf.ucw.cz>,
Andrea Arcangeli <andrea@suse.de>,
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 13:19:24 -0700 [thread overview]
Message-ID: <160380000.1030393164@flay> (raw)
In-Reply-To: <1030388713.2776.11.camel@irongate.swansea.linux.org.uk>
>> 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".
>
> Statistically irrelevant. When you have 100,000 samples all the
> pre-emption ones drop into the dud sample filter with IRQ disturbance
> and so on.
OK, so let's take a better example. People are (I think) mainly using rdtsc
to provide a monotonically increasing counter for database "transaction
order" stamping. I think that's really the case we're worried about.
M.
next prev parent reply other threads:[~2002-08-26 20:20 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
2002-08-26 19:00 ` Pavel Machek
2002-08-26 19:05 ` Alan Cox
2002-08-26 20:19 ` Martin J. Bligh [this message]
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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