From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Hirstius Date: Wed, 06 Apr 2005 07:29:59 +0000 Subject: Re: [Gelato-technical] Serious performance degradation on a RAID Message-Id: <42538FF7.60404@cern.ch> List-Id: References: <16978.62532.841151.100745@napali.hpl.hp.com> In-Reply-To: <16978.62532.841151.100745@napali.hpl.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org David Mosberger wrote: >>>>>>On Tue, 05 Apr 2005 20:11:51 +0200, Andreas Hirstius said: >>>>>> >>>>>> > > Andreas> Hi, We have a rx4640 with 3x 3Ware 9500 SATA controllers > Andreas> and 24x WD740GD HDD in a software RAID0 configuration > Andreas> (using md). With kernel 2.6.11 the read performance on the > Andreas> md is reduced by a factor of 20 (!!) compared to previous > Andreas> kernels. The write rate to the md doesn't change!! (it > Andreas> actually improves a bit). > >Is there any reason to believe this change in behavior is >ia64-specific? I doubt it. The q-syscollect profiles on your >web-site shows that the CPU is basically completely idle. You may >want to try 2.6.10 to see whether the bad behavior was introduced >before or after that. Unfortunately, 2.6 is developing very rapidly >so you may have to do more binary searching between 2.6.9 and 2.6.10 >or 2.6.10 and 2.6.11 to pin the problem down to a useful granularity. >You may also want to look at the bitkeeper changelogs to see if you >can find anything suspicious (you can do that easily via the web by >browsing the source code [1]). Lastly, you may want to ask on >linux-kernel whether anybody can think of a change that could have >this effect. > > > The problems started with 2.6.10-bk7... (and I've tested 2.6.9, 2.6.10, 2.6.10-bk5 - -bk14, 2.6.11-rc[1-5], 2.6.11, 2.6.11-mm[12], 2.6.12-rc[12]) The only other platform I have is a dual-xeon and I don't see the problem there (same controllers/disks)... Because of this strange correlation between block size and page size and the fact, that I don't see a problem on x86 I suspected an ia64-specific problem. My "favourite" candidate is the conversion to 4 level pagetables between 2.6.10-bk6 and 2.6.10-bk7. Andreas > --david > >[1] http://linux.bkbits.net:8080/linux-2.5/src?nav=index.html >- >To unsubscribe from this list: send the line "unsubscribe linux-ia64" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html > > >