From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from digeo-nav01.digeo.com (digeo-nav01.digeo.com [192.168.1.233]) by packet.digeo.com (8.9.3+Sun/8.9.3) with SMTP id QAA12048 for ; Wed, 9 Oct 2002 16:35:28 -0700 (PDT) Message-ID: <3DA4BC7B.EC8D65A3@digeo.com> Date: Wed, 09 Oct 2002 16:32:11 -0700 From: Andrew Morton MIME-Version: 1.0 Subject: Re: 2.5.40-mm1 References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Mala Anand Cc: lkml , "linux-mm@kvack.org" , Bill Hartner List-ID: Mala Anand wrote: > > ... > P4 Xeon CPU 1.50 GHz 4-way - hyperthreading disabled > Src is aligned and dst is misaligned as follows: > > Dst 2.5.40 2.5.40+patch 2.5.40+patch++ > Align throughout throughput throughput > (bytes) KB/sec KB/sec KB/sec > 0 1360071 1314783 912359 > 1 323674 340447 > 2 329202 336425 > 4 512955 693170 > 8 523223 615097 506641 > 12 517184 558701 553700 > 16 966598 872080 932736 > 32 846937 838514 845178 Note the tremendous slowdown which the P4 suffers when you're not cacheline aligned. Even 32-byte-aligned is down a lot. > I see too much variance in the test results so I ran > each test 3 times. I tried increasing the iterations > but it did not reduce the variance. > > Dst is aligned and src is misaligned as follows: > > Dst 2.5.40 2.5.40+patch > Align throughout throughput > (bytes) KB/sec KB/sec > 0 1275372 1029815 > 1 529907 511815 > 2 534811 530850 > 4 643196 627013 > 8 568000 626676 > 12 574468 658793 > 16 631707 635979 > 32 741485 592938 This differs a little from my P4 testing - the rep;movsl approach seemed OK for 8,16,32 alignment. But still, that's something we can tune later. > > However I have seen using floating point registers instead of integer > registers on Pentium IV improves performance to a greater extent on > some alignments. I need to do more testing and then I will create a > patch for pentium IV. I believe there are "issues" using those registers in-kernel. Related to the need to save/restore them, or errata; not too sure about that. -- 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/