From: "Richard B. Johnson" <root@chaos.analogic.com>
To: Ashwin Rao <ashwin_s_rao@yahoo.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: inconsistent do_gettimeofday for copy_page
Date: Wed, 10 Mar 2004 07:21:40 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.53.0403100719360.15264@chaos> (raw)
In-Reply-To: <20040310111919.83754.qmail@web10901.mail.yahoo.com>
On Wed, 10 Mar 2004, Ashwin Rao wrote:
> For calculating the time required to copy_page i tried
> the do_gettimeofday for 1000 pages in a loop. But as
> the number of pages changes the time required varies
> non-linearly.
> I also tried reading xtime and using monotonic_clock
> but they didnt help either. For do_gettimeof day for a
> single invocation of copy_page on a pentium 4 gave me
> 10 microsecs but when invoked for a 1000 pages the
> time required was 750ns per page.
> Is there some way of finding out the exact time
> required for copying a page.
>
> Ashwin
>
`rdtsc` on Intel. Gets total CPU clocks. Of course, you will
get jitter unless you disable interrupts during the procedure
you are measuring.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
Note 96.31% of all statistics are fiction.
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prev parent reply other threads:[~2004-03-10 12:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-10 11:19 Ashwin Rao
2004-03-10 11:35 ` Benjamin Herrenschmidt
2004-03-10 12:21 ` Richard B. Johnson [this message]
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