lkml.org 
[lkml]   [2012]   [Jan]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Bad SSD performance with recent kernels
From
Date
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.



--
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/

\
 
 \ /
  Last update: 2012-01-27 07:47    [W:0.119 / U:0.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site