From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030640AbWFVQb5 (ORCPT ); Thu, 22 Jun 2006 12:31:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030643AbWFVQb5 (ORCPT ); Thu, 22 Jun 2006 12:31:57 -0400 Received: from main.gmane.org ([80.91.229.2]:33744 "EHLO ciao.gmane.org") by vger.kernel.org with ESMTP id S1030640AbWFVQb4 (ORCPT ); Thu, 22 Jun 2006 12:31:56 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Andrey Melnikoff Subject: Re: Serial Console and Slow SCSI Disk Access? Date: Thu, 22 Jun 2006 20:18:54 +0400 Message-ID: References: <448DDC7F.4030308@mazunetworks.com> <448DDF1D.5020108@rtr.ca> <448DE4F1.9000407@mazunetworks.com> <4496492A.1030907@aitel.hist.no> <4496BF65.30108@mazunetworks.com> <44979F99.1090807@aitel.hist.no> X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: kenga.kmv.ru Cancel-Lock: sha1:W/TaZhS6BjZBBoEp07bSTqk9has= User-Agent: tin/1.8.2-20060425 ("Shillay") (UNIX) (Linux/2.6.17-rc2 (i686)) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Lang wrote: > On Tue, 20 Jun 2006, Helge Hafting wrote: > > Jeff Gold wrote: > >> Helge Hafting wrote: > >>> With nothing attached, any write to the serial device might go > >>> through a lengthy timeout because of flow control. [...] But I can't > >>> see why it'd make scsi disks slower. The scsi host adapter initialization > >>> writes some messages of course, but there should be no > >>> more console accesses during a hdparm test run. > >> > >> This makes sense to me. When I attach a serial cable and use that to login > >> (I've got agetty running), hdparm produces no console messages that I can > >> see using minicom. Still, the disk throughput is around 1.5 MB/sec for > >> some reason. When I disable the serial console in grub.conf and reboot I > >> get over 70 MB/sec again. > >> > >> A combination of out-of-tree patches (mainly network related but also one > >> to disable PM_TIMERS) seem to eliminate the issue even with the serial > >> console enabled, at least for the moment. That means I no longer have a > >> problem, but the whole thing is mysterious to me. > > I can see one possibility, that I didn't think of yesterday. > > Do the scsi host adapter share its interrupt with the serial line? > > (Boot a kernel that has the problem, and when scsi is slow, do a > > cat /proc/interrupts > > If the scsi and the serial driver share an interrupt, then that is the source > > of the problem. [skipp] > I ran into a similar problem (extremely slow scsi performance), but hadn't > reported it as I made a lot of changes at the same time (moved from 2.6.7 to > 2.6.12.3 as well as enabling the serial console). but with this report I wanted > to chime in with a weak 'me-too'. I haven't rebooted without the serial console > yet to confirm this, but I will do so shortly, and try 2.6.17 to see if it has a > similar problem or not. 2.6.17.1 here, MB Intel SCB20, aic7899 onboard. aic7xxx compilled in, serial core compilled in, serial console enabled. With/without serial sonsole - speed 66.0 Mb/s. Maybe problem related to MB chipset?