[Bug 131094] Re: Heavy Disk I/O harms desktop responsiveness

Tue Apr 21 11:02:49 UTC 2009

Milan wrote:
> Thanks for these detailed informations. So you suggest that the IO
> scheduler is not giving enough priority to tasks other than the file
> copy; that's an interesting way of finding the cause of the problem,
> indeed! I suggest you try the new kernel, and if it's not fixed, go to
> the upstream report and explain them your case. You can find many
> different scripts to test the system's responsiveness there, and you'll
> notice that's really tricky (long thread...).

I suggest it's not just about giving I/O priority to tasks other than
the copy, but also giving them enough "anticipatory" time so there
isn't a pair of head seeks for every I/O operation by the non-copying
tasks.

It has to look like this to be efficient:

    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
                <head seeks>
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                <head seeks>
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
    I/O for copy
                <head seeks>
                           I/O for other thing
                           I/O for other thing
                           I/O for other thing
                etc.

And not

    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
    I/O for copy
                <head seeks>
                           I/O for other thing
                <head seeks>
                etc.

-- 
Heavy Disk I/O harms desktop responsiveness
https://bugs.launchpad.net/bugs/131094
You received this bug notification because you are a member of Kernel
Bugs, which is subscribed to Linux.