From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugme-daemon@bugzilla.kernel.org Subject: [Bug 10846] Slow write on LSISAS1068E (SAS6/iR) on kernel >= 2.6.22 Date: Tue, 3 Jun 2008 00:00:49 -0700 (PDT) Message-ID: <20080603070049.B682411D108@picon.linux-foundation.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:36575 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753345AbYFCHAv convert rfc822-to-8bit (ORCPT ); Tue, 3 Jun 2008 03:00:51 -0400 Received: from picon.linux-foundation.org (picon.linux-foundation.org [140.211.169.79]) by smtp1.linux-foundation.org (8.14.2/8.13.5/Debian-3ubuntu1.1) with ESMTP id m5370nOV019694 for ; Tue, 3 Jun 2008 00:00:50 -0700 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org http://bugzilla.kernel.org/show_bug.cgi?id=3D10846 ------- Comment #3 from dom.lalot@gmail.com 2008-06-03 00:00 ------- James and Roland Sure there's write cache enabled and your remark make sense. That's the= first thing I noticed when changing kernel. We went from 2.8.18 SCSI device sda: drive cache: write through SCSI device sda: 285155328 512-byte hdwr sectors (146000 MB) testing with kernels 2.6.22 or 2.6.24, we noticed a change about the wr= ite cache, just changing the kernel on the same hardware. [ 115.986031] sd 4:1:0:0: [sdb] Write cache: disabled, read cache: ena= bled, doesn't support DPO or FUA [ 115.986494] sd 4:1:0:0: [sdb] 285155328 512-byte hardware sectors (1= 46000 MB) So we got a utility lsiutil to change the settings in the firmware abou= t write cache, and we saw then write cache: enabled, but the speed stayed slow. We also took a driver from lsi About your remarks, I tested again using dd with a larger file (when un= taring the kernel there's also a difference but it is less basic than dd) The way dd reports its speed may be not very accurate I agree, but it = does not change from a kernel point of view. Linux debian-test.pr.univmed.fr 2.6.21.7 debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 100000 100000+0 enregistrements lus 100000+0 enregistrements =C3=A9crits 1024000000 octets (1,0 GB) copi=C3=A9s, 5,39271 seconde, 190 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 100000 100000+0 enregistrements lus 100000+0 enregistrements =C3=A9crits 1024000000 octets (1,0 GB) copi=C3=A9s, 5,45364 seconde, 188 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 200000 200000+0 enregistrements lus 200000+0 enregistrements =C3=A9crits 2048000000 octets (2,0 GB) copi=C3=A9s, 23,0492 seconde, 88,9 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 200000 200000+0 enregistrements lus 200000+0 enregistrements =C3=A9crits 2048000000 octets (2,0 GB) copi=C3=A9s, 22,5306 seconde, 90,9 MB/s I reboot and change kernel: debian-test:~# uname -a Linux debian-test.pr.univmed.fr 2.6.22.19 #1 SMP Fri May 30 19:53:56 CE= ST 2008 i686 GNU/Linux debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 100000 100000+0 enregistrements lus 100000+0 enregistrements =C3=A9crits 1024000000 octets (1,0 GB) copi=C3=A9s, 13,9614 seconde, 73,3 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 100000 100000+0 enregistrements lus 100000+0 enregistrements =C3=A9crits 1024000000 octets (1,0 GB) copi=C3=A9s, 13,9406 seconde, 73,5 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 200000 200000+0 enregistrements lus 200000+0 enregistrements =C3=A9crits 2048000000 octets (2,0 GB) copi=C3=A9s, 29,3472 seconde, 69,8 MB/s debian-test:~# dd if=3D/dev/zero of=3D/root/test.cdrom bs=3D10k count=3D= 200000 200000+0 enregistrements lus 200000+0 enregistrements =C3=A9crits 2048000000 octets (2,0 GB) copi=C3=A9s, 29,1689 seconde, 70,2 MB/s debian-test:~# (I believe that, if I take a bigger file, we will get the same speed, t= he difference is due to the first data going to write cache) What can we see: 1. having a larger file make the write cache less efficient (normal) 2. It seems that the write caching is no more working from 2.6.22 on ou= r hardware (new blade servers from Dell m600). Even using firmware utilit= ies didn't improve the speed. LSI firmware does not activate write cache an= d their BIOS has no setup for that. Switching from 2.6.18 to 2.6.22 makes the k= ernel=20 no more doing write cache. Changing in the firmware activate something.= =2E just in dmesg, we see it: enabled again, but in fact there's no speed differ= ence. My subject should have been: no more write caching --=20 Configure bugmail: http://bugzilla.kernel.org/userprefs.cgi?tab=3Demail ------- You are receiving this mail because: ------- You are the assignee for the bug, or are watching the assignee. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html