On Sat, Jan 28, 2012 at 08:51:08PM +0800, Wu Fengguang wrote: > 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 so we have intel vs samsung here ... > 87:00.0 Serial Attached SCSI controller: LSI Logic / Symbios > Logic SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] (rev 02) ... and sas vs sata >> 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.. will do tonight! >> 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...) attached the files as .txz thanks, Herbert > 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@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/