lkml.org 
[lkml]   [2009]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: I/O and pdflush
    Hi Fernando,

    What's your SSD's IO parameters? Ie. output of this command:

    grep -r . /sys/block/sda/queue/

    Please replace 'sda' with your SSD device name.

    Thanks,
    Fengguang

    On Mon, Aug 31, 2009 at 09:24:20PM +0800, Fernando Silveira wrote:
    > On Sat, Aug 29, 2009 at 07:21, Wu Fengguang<fengguang.wu@intel.com> wrote:
    > > On Sat, Aug 29, 2009 at 06:12:47PM +0800, Wu Fengguang wrote:
    > >> On Sat, Aug 29, 2009 at 05:48:40AM +0800, Fernando Silveira wrote:
    > >> > On Sun, Jul 12, 2009 at 05:04, Wu Fengguang<fengguang.wu@intel.com> wrote:
    > >> > > On Sat, Jul 11, 2009 at 02:27:25PM -0300, Fernando Silveira wrote:
    > >> > >> I'm having a hard time with an application that writes sequentially
    > >> > >> 250GB of non-stop data directly to a solid state disk (OCZ SSD CORE
    > >> > >> v2) device and I hope you can help me. The command "dd if=/dev/zero
    > >> > >> of=/dev/sdc bs=4M" reproduces the same symptoms I'm having and writes
    > >> > >> exactly as that application does.
    > >>
    > >> Sure. Attached is a writeback debug patch. It will generate lots of
    > >> kernel messages. You can just stop your klogd, start your workload
    > >> and monitor the SSD writeback throughput via tools like iostat/dstat.
    > >
    > > Fernando, will you post the output of iostat/dstat too? Thanks!
    > > The ssd-no_dirty_buffer_with_random_192mb_writes.png is a good overview,
    > > however I'd like to also check out the numbers for each second :)
    > >
    > >> When it goes into the suboptimal 25MB/s state for several seconds, run
    > >>         dmesg > dmesg-writeback
    > >> and send me the log.
    > >>
    > >> And it is advised to turn on the kconfig option CONFIG_PRINTK_TIME=y.
    >
    > Thanks for your help.
    >
    > You can reach in the URL below a tarball which contains the data I
    > logged after patching the kernel with only your last patch.
    >
    > http://rootshell.be/~swrh/ssd-tests/log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M.tar.gz
    >
    > Each file contained in the tarball is described below:
    >
    > - log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M-{0-ddv,1-table,2-plot}.*
    > Logging statistics. The "0-ddv" file is the log of a modified
    > version of the dd(1) utility to print writing statistics after every
    > write(2), "1-table" is a table version of the "0-ddv" file parsed with
    > awk(1) and "2-plot" is the a plot image of the writing statistics.
    >
    > - log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M-0-dstat.log
    > The result of "dstat > dstat.log" executed ~3 seconds after "ddv" started.
    >
    > - log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M-0-iostat.log
    > The result of "iostat 1 > iostat.log" executed ~15 seconds after
    > "ddv" started.
    >
    > - log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M-0-dmesg_writeback_{1..67}.log
    > The result of "for i in {1..67}; do dmesg > dmesg-writeback-$i.log;
    > sleep 1; done" executed when "ddv" had written about 42GB of data.
    >
    > - log-20090831_0908-MK020903042C0001B-prosar_fcc2-bs_4M-0-dmesg_writeback_{100..186}.log
    > The result of "for i in {100..186}; do dmesg >
    > dmesg-writeback-$i.log; sleep 1; done" executed when "ddv" had written
    > about 51GB of data.
    >
    > Please tell me if you need anything else. I could make a more
    > synchronized or informative logging output if you need.
    >
    > Best regards,
    >
    > --
    > Fernando Silveira <fsilveira@gmail.com>
    --
    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: 2009-08-31 16:03    [W:0.051 / U:95.352 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site