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Date: Sat, 28 Jan 2012 20:51:08 +0800 From: Wu Fengguang <wfg@...ux.intel.com> To: Herbert Poetzl <herbert@...hfloor.at> Cc: Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org> Subject: Re: Bad SSD performance with recent kernels Hi Herbert, On Fri, Jan 27, 2012 at 07:00:34AM +0100, Herbert Poetzl wrote: > > 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 Thanks for the through tests! However I cannot reproduce the regressions, but see slightly better performance in 3.2: Linux lkp-nex04 3.2.0-rc7-shli+ #121 SMP Thu Jan 19 18:10:45 CST 2012 x86_64 x86_64 x86_64 GNU/Linux 21474836480 bytes (21 GB) copied, 90.9307 s, 236 MB/s real = 91.03, user = 0.01, sys = 25.80, 28% cpu 21474836480 bytes (21 GB) copied, 90.8864 s, 236 MB/s real = 90.90, user = 0.01, sys = 25.54, 28% cpu 21474836480 bytes (21 GB) copied, 93.4684 s, 230 MB/s real = 93.47, user = 0.02, sys = 25.12, 26% cpu Linux lkp-nex04 2.6.38 #334 SMP Sat Jan 28 20:16:25 CST 2012 x86_64 GNU/Linux 21474836480 bytes (21 GB) copied, 96.2382 s, 223 MB/s real = 96.29, user = 0.01, sys = 57.64, 59% cpu 21474836480 bytes (21 GB) copied, 96.5796 s, 222 MB/s real = 96.60, user = 0.02, sys = 58.08, 60% cpu 21474836480 bytes (21 GB) copied, 95.486 s, 225 MB/s real = 95.51, user = 0.00, sys = 58.20, 60% cpu My test box has 64GB memory and a dozen 80GB INTEL SSDSA2M080G2GN SSD drives attached to 87:00.0 Serial Attached SCSI controller: LSI Logic / Symbios Logic SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] (rev 02) > 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 ... Would you please create a filesystem and large file on sda and run the tests on the file? There was some performance bug on reading the raw /dev/sda device file.. > The detailed test results as well as the dmesg and config > of each kernel can be found here: > http://vserver.13thfloor.at/Stuff/SSD It would be better for such files be attached in future. (For one thing I get timeout when trying to open the link...) Thanks, Fengguang > 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 > > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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