From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 10 Mar 2004 07:21:40 -0500 (EST) From: "Richard B. Johnson" Reply-To: root@chaos.analogic.com Subject: Re: inconsistent do_gettimeofday for copy_page In-Reply-To: <20040310111919.83754.qmail@web10901.mail.yahoo.com> Message-ID: References: <20040310111919.83754.qmail@web10901.mail.yahoo.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Ashwin Rao Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org