Mailinglist Archive: opensuse (1986 mails)

["Carlos E. R." <robin.listas@xxxxxxxxxxxxxx>]

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On Tuesday, 2008-11-18 at 16:42 -0800, James D. Parra wrote:

> Trying to find why almost every process that requires IO has near 100% wait
> times.
>
> Even a simple 'cp' command has enormous wait times and doesn't appear at or
> near the top of the     list when running 'top'. This was occurring when
> writing to a raid, but have tested writing to the system drive and the same
> thing occurs.
>
> Running the 'cp command copying a 19GB file from /tmp/file1 /tmp/file2 will
> take 50 minutes

Not normal.

> Mem:  33020488k total,  5782932k used, 27237556k free,      316k buffers
> Swap:  8393952k total,        0k used,  8393952k free,  5562388k cached

No used swap, lots of cached memory, lots of free memory...

>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
>    1 root      20   0   864  336  272 S    0  0.0   0:01.28 init
>    2 root      15  -5     0    0    0 S    0  0.0   0:00.00 kthreadd
>    3 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/0
>    4 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/0
>    5 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/1
>    6 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/1
>    7 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/2
>    8 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/2
>    9 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/3
>   10 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/3
>   11 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/4
>   12 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/4
>   13 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/5
>   14 root      15  -5     0    0    0 S    0  0.0   0:00.00 ksoftirqd/5
>   15 root      RT  -5     0    0    0 S    0  0.0   0:00.00 migration/6
> <snip>

What is that "migration" task? Raid migration, perhaps? I'm wild guessing, 
but if that is a task copying from one mirror to another or such, it would 
explain the problem. That "migration" runs at Real Time priority, I think.

> 'cp' is not showing up, but it is running;
>
> root      3915  0.2  0.0   8296   696 pts/0    D+   15:20   0:02 cp file1
> file2

There is an option in "top" to show at what function it is waiting.

- -- 
Cheers,
       Carlos E. R.

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