Messages in this thread | | | From | Fernando Silveira <> | Date | Mon, 31 Aug 2009 10:24:20 -0300 | Subject | Re: I/O and pdflush |
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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/
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