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[RFC] blkio_delay_total is calculated mistakenly

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Hi,

When I read Linux Kernel source codes about how "blkio_delay_total"
(delay waiting for synchronous block I/O to complete for one task) is
calculated in Linux/kernel/delayacct.c file [1], I find that
"blkio_delay_total" adds "task->delays->blkio_delay" to be the total
delay time for one task to wait for synchronous I/O dynamically but
"tsk->delays->blkio_delay" has already been calculated as the total
delay time that one task is waiting for synchronous I/O [2]
dynamically. I think "blkio_delay_total" should not add
"task->delays->blkio_delay" since "task->delays->blkio_delay" is
already the total delay time we want.

Am I missing anything?

BTW, the patch in the attachment may solve this problem if I don't
miss anything. Thank you.


[1] http://lxr.free-electrons.com/source/kernel/delayacct.c?v=4.7#L121
[2] http://lxr.free-electrons.com/source/kernel/delayacct.c?v=4.7#L52

Thanks,
Weiwei Jia

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[RFC] blkio_delay_total is calculated mistakenly Weiwei Jia <harrynjit@gmail.com> - 2017-02-15 02:30 +0100
  Re: [RFC] blkio_delay_total is calculated mistakenly Greg KH <gregkh@linuxfoundation.org> - 2017-02-15 04:10 +0100
    Re: [RFC] blkio_delay_total is calculated mistakenly Weiwei Jia <harrynjit@gmail.com> - 2017-02-15 04:20 +0100

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