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Thread: Nearly 100% CPU usage when writing to disk

  1. #1

    Default Nearly 100% CPU usage when writing to disk

    Hi,

    I have experienced an issue when running applications which write huge amount of data to the hard disk. E. g. extracting files with Ark, downloading with KTorrent at ~10 MiB/s, or even copying large files. Running such an operation makes the CPU running at nearly 100%, and the systems becomes unusable, becouse everything starts to lag (even the mouse cursor).

    I am using openSUSE 13.1 with KDE 4.12.2 and 3.11.10-7-desktop kernel.

    Is there anyone who experiencing this problem?

  2. #2

    Default Re: Nearly 100% CPU usage when writing to disk

    I also have the system freezing completely at times but not when writing large files, so far on my side is un-explainable, my main suspect is the gpu driver.

  3. #3
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    Default Re: Nearly 100% CPU usage when writing to disk

    Quote Originally Posted by helmet91 View Post
    I have experienced an issue when running applications which write huge amount of data to the hard disk. E. g. extracting files with Ark, downloading with KTorrent at ~10 MiB/s, or even copying large files.
    Is the file on an NTFS file system? In my experience, the CPU cost for NTFS activity is higher than with native linux file systems, though I have not seen it reach 100%.
    openSUSE Leap 15.2; KDE Plasma 5.18.5;

  4. #4

    Default Re: Nearly 100% CPU usage when writing to disk

    No, it is on ext4 filesystem.

  5. #5
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    Default Re: Nearly 100% CPU usage when writing to disk

    On 2014-02-22 09:06, helmet91 wrote:
    >
    > No, it is on ext4 filesystem.


    There are some people reporting similar problems, but still nothing
    definite has been found. No known culprit yet.

    If this happened a decade ago, I would immediately suspect that the
    system is not using DMA to access the disks...

    Try hdparm -i and -I on that disk. It should verify if dma is used, and
    which.


    Oh, I forgot. One culprit was found in one or two cases: the graphical
    environment desktop or file browser. Try to copy the files using 'mc'
    instead in an xterm or console. You will probably have to install it.
    Very fast and powerful _text_ mode file browser.

    --
    Cheers / Saludos,

    Carlos E. R.

    (from 13.1 x86_64 "Bottle" (Minas Tirith))

  6. #6

    Default re: Nearly 100% CPU usage when writing to disk

    Thank you for your answer.


    Quote Originally Posted by robin_listas View Post
    Try hdparm -i and -I on that disk. It should verify if dma is used, and which.

    Regarding to hdparm, the hard disk in question uses udma6 (here is the output of hdparm).


    Quote Originally Posted by robin_listas View Post
    Try to copy the files using 'mc' instead in an xterm or console.

    I have tried copying with mc, but the issue is still there.

  7. #7
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    Default Re: Nearly 100% CPU usage when writing to disk

    On 2014-02-22 14:06, helmet91 wrote:

    > robin_listas;2626471 Wrote:
    >>
    >> Try to copy the files using 'mc' instead in an xterm or console.
    >>

    >
    >
    > I have tried copying with mc, but the issue is still there.


    Oh.
    Then I'm out of ideas...

    Hum. Start a terminal and run 'top' in it. What process is eating the
    cpu time during copies?

    --
    Cheers / Saludos,

    Carlos E. R.

    (from 13.1 x86_64 "Bottle" (Minas Tirith))

  8. #8

    Default re: Nearly 100% CPU usage when writing to disk

    Always the one which performs the disk-write action. E. g. when I copy with mc, then mc. When I extract a RAR archive with Ark, then unrar. When I split a huge file into seperate parts, then split.

  9. #9
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    Default Re: Nearly 100% CPU usage when writing to disk

    On 02/22/2014 07:46 AM, helmet91 wrote:
    >
    > Always the one which performs the disk-write action. E. g. when I copy
    > with mc, then mc. When I extract a RAR archive with Ark, then unrar.
    > When I split a huge file into seperate parts, then split.


    Under top, what percentage of the time is consumed by the user (labeled us), the
    system (sy), or waiting (wa)? Copying a 4 GB file using cp in a console occupies
    about 20% sy and 33% wa on my system.


  10. #10

    Default re: Nearly 100% CPU usage when writing to disk

    Quote Originally Posted by lwfinger View Post
    Under top, what percentage of the time is consumed by the user (labeled us), the
    system (sy), or waiting (wa)? Copying a 4 GB file using cp in a console occupies
    about 20% sy and 33% wa on my system.
    us: 1.9%, sy: 3.1%, wa: 65%

    So, something may be wrong.

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