From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753129Ab2A0Go4 (ORCPT ); Fri, 27 Jan 2012 01:44:56 -0500 Received: from mail-ww0-f44.google.com ([74.125.82.44]:43586 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750948Ab2A0Goz (ORCPT ); Fri, 27 Jan 2012 01:44:55 -0500 Message-ID: <1327646687.2919.26.camel@edumazet-laptop> Subject: Re: Bad SSD performance with recent kernels From: Eric Dumazet To: Herbert Poetzl Cc: Linux Kernel ML Date: Fri, 27 Jan 2012 07:44:47 +0100 In-Reply-To: <20120127060034.GG29272@MAIL.13thfloor.at> References: <20120127060034.GG29272@MAIL.13thfloor.at> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 8bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le vendredi 27 janvier 2012 à 07:00 +0100, Herbert Poetzl a écrit : > Dear Community! > > Recently I decided to update the kernel on a Dell Laptop to > a more recent version than 2.6.38.x, but experienced bad > I/O performance with the new kernel, so I started to dig > a little deeper and ended up with the following test: > > 1) download and extract kernel (on 2.6.38.8) > 2) make defconfig > 3) make localmodconfig > 4) make > 5) make modules_install install > > Then I booted each kernel in single user and ran the following > test script: > > echo noop >/sys/class/block/sda/queue/scheduler > for n in 1 2 3; do sync; echo $n > /proc/sys/vm/drop_caches; done > /usr/bin/time -f "real = %e, user = %U, sys = %S, %P cpu" \ > ionice -c0 nice -20 \ > dd if=/dev/sda of=/dev/null bs=1M count=20480 > > echo deadline >/sys/class/block/sda/queue/scheduler > for n in 1 2 3; do sync; echo $n > /proc/sys/vm/drop_caches; done > /usr/bin/time -f "real = %e, user = %U, sys = %S, %P cpu" \ > ionice -c0 nice -20 \ > dd if=/dev/sda of=/dev/null bs=1M count=20480 > > echo cfq >/sys/class/block/sda/queue/scheduler > for n in 1 2 3; do sync; echo $n > /proc/sys/vm/drop_caches; done > /usr/bin/time -f "real = %e, user = %U, sys = %S, %P cpu" \ > ionice -c0 nice -20 \ > dd if=/dev/sda of=/dev/null bs=1M count=20480 > > > note that the Laptop is a relatively modern Latitude E6400 > with a Samsung 830 Series 256GB SSD > > here are the surprising results: > > @ linux 2.6.38.8 > 248 MB/s real = 86.74, user = 0.01, sys = 21.65, 24% cpu > 248 MB/s real = 86.81, user = 0.02, sys = 21.75, 25% cpu > 251 MB/s real = 85.63, user = 0.01, sys = 22.24, 25% cpu > > @ linux 2.6.39.4 > 49.0 MB/s real = 438.79, user = 0.01, sys = 19.79, 4% cpu > 25.7 MB/s real = 836.70, user = 0.02, sys = 18.39, 2% cpu > 27.7 MB/s real = 776.53, user = 0.01, sys = 16.03, 2% cpu > > @ linux 3.0.18 > 48.9 MB/s real = 439.07, user = 0.01, sys = 17.55, 4% cpu > 25.0 MB/s real = 859.03, user = 0.01, sys = 16.97, 1% cpu > 49.8 MB/s real = 431.61, user = 0.01, sys = 16.68, 3% cpu > > @ linux 3.1.10 > 54.0 MB/s real = 398.23, user = 0.01, sys = 17.36, 4% cpu > 29.4 MB/s real = 731.47, user = 0.01, sys = 17.14, 2% cpu > 25.0 MB/s real = 859.35, user = 0.01, sys = 14.51, 1% cpu > > @ linux 3.2.2 > 45.8 MB/s real = 468.85, user = 0.01, sys = 17.11, 3% cpu > 44.8 MB/s real = 478.92, user = 0.01, sys = 17.02, 3% cpu > 45.0 MB/s real = 476.91, user = 0.01, sys = 16.14, 3% cpu > > > I have no idea why the I/O performance is that bad on any > kernel newer than 2.6.38.x, but I'm happy to test and/or > try various configurations as time permits ... > > The detailed test results as well as the dmesg and config > of each kernel can be found here: > http://vserver.13thfloor.at/Stuff/SSD > > many thanks in advance, > Herbert > > here some technical information: > > http://www.dell.com/us/dfb/p/latitude-e6400/pd > SATA controller: Intel Corporation ICH9M/M-E SATA AHCI Controller (rev 03) > > http://www.samsung.com/uk/consumer/memory-cards-hdd-odd/ssd/ssd/MZ-7PC256N/EU-spec > Model=SAMSUNG SSD 830 Series, FwRev=CXM03B1Q > supposed 520MB/s seq. read, 320MB/s seq. write, 75K IOPS > > I confirm I just noticed this on a brand new SSD from Crucial (128 GB) and a Dell E6400 too (3.5 years old model) The Ubuntu upgrade from 11.04 to 11.10 switched kernel (from 2.6.38.X to 3.0.0.X) and raw SSD performance (hdparm -t /dev/sda) dropped from 200 MB/s to 140 MB/s or so.