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

    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







    \
     
     \ /
      Last update: 2012-01-27 07:31    [W:0.024 / U:0.176 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site