Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759153AbXFVQVx (ORCPT ); Fri, 22 Jun 2007 12:21:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758131AbXFVQVq (ORCPT ); Fri, 22 Jun 2007 12:21:46 -0400 Received: from viefep18-int.chello.at ([213.46.255.22]:31257 "EHLO viefep17-int.chello.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758105AbXFVQVq (ORCPT ); Fri, 22 Jun 2007 12:21:46 -0400 Date: Fri, 22 Jun 2007 18:21:42 +0200 From: Carlo Wood To: Arjan van de Ven Cc: Jeff Garzik , linux-kernel@vger.kernel.org Subject: Re: SATA Harddisk speed drop of 100 MB/s Message-ID: <20070622162142.GA603@alinoe.com> Mail-Followup-To: Carlo Wood , Arjan van de Ven , Jeff Garzik , linux-kernel@vger.kernel.org References: <20070620224847.GA5488@alinoe.com> <4679B2DE.9090903@garzik.org> <1182397012.2863.0.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1182397012.2863.0.camel@laptopd505.fenrus.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2646 Lines: 84 On Wed, Jun 20, 2007 at 08:36:52PM -0700, Arjan van de Ven wrote: > also do a > > echo 60 > /proc/sys/vm/dirty_ratio > > first to see if that helps That makes no difference. It took a while before I replied - because I first want to do a bisect to find a version closer to the problem. So far I found out that it's RAID only. I have four disks: Three times a western digital Raptor 10k rpm: ATA device, with non-removable media Model Number: WDC WD740ADFD-00NLR1 Firmware Revision: 20.07P20 And one Seagate Barracuda 7200 rpm: ATA device, with non-removable media Model Number: ST3320620AS Firmware Revision: 3.AAE The Raptors are in RAID5. hdparm -tT gives me always > 4 GB/s cached reads, for example: Timing cached reads: 8166 MB in 2.00 seconds = 4086.82 MB/sec and the buffered disk reads do not significantly vary when reading the devices directly (/dev/sda, /dev/sdb, /dev/sdc for the Raptors and /dev/sdd for the Barracuda): /dev/sda etc: Around 67 MB/sec /dev/sdd : Around 75 MB/sec (so much for 10k rpm ...) These numbers are weird in itself (the 67 should have been 75, and the 75 should have been 54) - but at least they are constant. What DOES *signficantly* change as function of kernel revision is the buffered disk read with hdparm -tT /dev/md2 The normal speed I get is > 160, often 165 MB/sec. But with kernel revisions over a certain version that drops to around 67 MB/sec - and at one point I even observed a drop in speed every time I repeated the measurement until the speed was around 30 MB/s ! At the moment I am (still) doing the bisect; I had some problems compiling a pristine 2.6.18 and some problems with the config (that differs significantly between 2.6.18 and 2.6.22) as well as the problem that the kernel simply didn't compile for a large range of revisions needed for the bisect (I needed to export current_is_keventd with this patch: diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c525731..012e11b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -654,6 +654,7 @@ int current_is_keventd(void) return ret; } +EXPORT_SYMBOL_GPL(current_is_keventd); /* Take the work from this (downed) CPU. */ static void take_over_work(struct workqueue_struct *wq, unsigned int cpu) ) I'll report back when I'm done with the bisect :) -- Carlo Wood - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/