Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Linux 3.16: Deadline I/O Scheduler Generally Leads With A SSD

  1. #1
    Join Date
    Jan 2007
    Posts
    14,653

    Default Linux 3.16: Deadline I/O Scheduler Generally Leads With A SSD

    Phoronix: Linux 3.16: Deadline I/O Scheduler Generally Leads With A SSD

    There's been numerous requests lately for more disk I/O scheduler benchmarks on Phoronix of the Linux kernel and its various scheduler options. Given that there's routinely just speculation and miscommunication by individuals over the best scheduler for HDDs/SSDs, here's some fresh benchmarks for reference using the Linux 3.16 kernel.

    http://www.phoronix.com/vr.php?view=20638

  2. #2
    Join Date
    Oct 2012
    Location
    Sweden
    Posts
    302

    Default

    Quote Originally Posted by phoronix View Post
    Phoronix: Linux 3.16: Deadline I/O Scheduler Generally Leads With A SSD

    There's been numerous requests lately for more disk I/O scheduler benchmarks on Phoronix of the Linux kernel and its various scheduler options. Given that there's routinely just speculation and miscommunication by individuals over the best scheduler for HDDs/SSDs, here's some fresh benchmarks for reference using the Linux 3.16 kernel.

    http://www.phoronix.com/vr.php?view=20638
    This is interesting, I seem to recall Noop being the fastest on SSDs? I might need to change my Udev rule now.

  3. #3
    Join Date
    Apr 2010
    Location
    France
    Posts
    16

    Default

    I don't understand how you can conclude that it's the SSD that makes deadline faster since you didn't test any HDD. Maybe it's the same story with a HDD and the difference between the schedulers lies somewhere else.

  4. #4
    Join Date
    Feb 2013
    Posts
    314

    Default

    Is Deadline the default I/O scheduler in Linux?

  5. #5
    Join Date
    Oct 2012
    Location
    Sweden
    Posts
    302

    Default

    Quote Originally Posted by peppercats View Post
    Is Deadline the default I/O scheduler in Linux?
    No it's CFQ. He has done benchmarks before that shows that CFQ is the fastest in most scenarios on HDDs.

  6. #6
    Join Date
    Aug 2012
    Location
    Pennsylvania, United States
    Posts
    1,877

    Default

    Quote Originally Posted by peppercats View Post
    Is Deadline the default I/O scheduler in Linux?
    On Ubuntu I think it is. The other distros and the kernel all default to CFQ, I think.

  7. #7
    Join Date
    Feb 2013
    Posts
    314

    Default

    Quote Originally Posted by xeekei View Post
    No it's CFQ. He has done benchmarks before that shows that CFQ is the fastest in most scenarios on HDDs.
    so if I only use an SSD I should switch to deadline?

  8. #8
    Join Date
    Oct 2012
    Location
    Sweden
    Posts
    302

    Default

    Quote Originally Posted by peppercats View Post
    so if I only use an SSD I should switch to deadline?
    It seems so. It's possible to write a udev rule that detects if it's a rotational medium or solid state, and set the scheduler accordingly. I have Noop for SSDs and CFQ for HDDs. I think it will choose Noop for USB thumbsticks and the like too.

  9. #9
    Join Date
    Mar 2013
    Posts
    16

    Default

    I have a eepc notebook with extremely slow SSD. What I've noted over the years is that I don't really care how fast the disk is, but whether or now the desktop remains responsive when a backgroud process is pounding the disk. Typically, can I continue web browsing while synaptic/apt is updating packages?

    In the above scenario I've noted that changing scheduling and priority for synaptic and children had a large effect. Also note that on the same machine with windows xp while starting firefox/thunderbird the machine, even the mouse pointer freezes for 10 - 30 sec. (due to long stall caused by windows fsync equivalent), while doing the same on Linux is workable.

    I wonder if such a scenario if sufficiently convered by the bench marks.

  10. #10

    Default

    CFQ is supposedly already tweaked for SSDs.

    From https://www.kernel.org/doc/Documenta...fq-iosched.txt

    CFQ has some optimizations for SSDs and if it detects a non-rotational
    media which can support higher queue depth (multiple requests at in
    flight at a time), then it cuts down on idling of individual queues and
    all the queues move to sync-noidle tree and only tree idle remains. This
    tree idling provides isolation with buffered write queues on async tree.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •