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SubjectRe: [PATCH] LatencyTop: make reason (blk_execute_rq+0x7a/0xd) known
Arjan van de Ven wrote:
> Török Edwin wrote:
>>
>> Cause Maximum
>> Average
>> SCSI device ioctl 34.2 msec
>> 14.4 msec
>
> great! I'll put this into my patchkit!

Thanks.

>> I also noticed some unsigned overflows, my top latency was sometimes a
>> very large number (18................................), which
>> was probably -1, or some other negative number. I haven't found a way
>> to reproduce it yet (it happens very rarely).
>
>
> I've not seen this; I'll take another peak at the code.

I just captured this:

Cause Maximum Average
Waiting for userspace lock 18446744073638300.0
msec 9223372036783524.0 msec
Waiting for processes to die (waitpid) 18446744073638296.0
msec 9223372036783520.0 msec
Waiting for event (poll) 18446744073565216.0
msec 764505121372.0 msec
SCSI device ioctl 35.2 msec
13.7 msec
Application requested delay 19.5 msec
0.0 msec
page fault 18.6 msec
4.0 msec
Reading from file 16.6 msec
1.5 msec
Waiting for buffer IO 15.2 msec
3.0 msec
mutex lock 15.0 msec
15.0 msec

I was also looking at /proc/latency_stats using watch, and I've seen
that there were negative number.
Unfortunately I couldn't copy+paste it, because it was gone too fast.

I was running a program with 4 threads doing usleep(0) in an inf-loop.
However I can't reproduce the overflow now with the same program.

Best regards,
--Edwin
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