Re: high load with usb device

[Avi Kivity <avi@redhat.com>]

  On 09/14/2010 12:00 PM, Michael Tokarev wrote:
>   # strace -p 23020 -p 23023 -c
> Process 23020 attached - interrupt to quit
> Process 23023 attached - interrupt to quit
> ^CProcess 23020 detached
> Process 23023 detached
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
>   98.98   23.462158       15569      1507           ioctl
>    0.64    0.151725          37      4063         5 futex
>    0.11    0.025051           0     86932           select
>    0.09    0.021188           0    408836           clock_gettime
>    0.07    0.016543           0    271933    136484 read
>    0.04    0.008958           0    181118           gettimeofday
>    0.02    0.005756           0    101190           write
>    0.02    0.005506           0     89180           timer_settime
>    0.02    0.004754           0     96271           timer_gettime
>    0.01    0.002682           0     50595           rt_sigaction
>    0.00    0.000000           0         1           rt_sigpending
>    0.00    0.000000           0         1         1 rt_sigtimedwait
> ------ ----------- ----------- --------- --------- ----------------
> 100.00   23.704321               1291627    136490 total
>
>

Well, well.  Translating to rates, we have 63.6 ioctls/sec but 17k 
clock_gettime, 11k read() and 4k writes per second.  The device model 
has gone haywire, somehow without any trace in perf top.

Let's see what those reads and writes are about.  Please strace a short 
segment again, without -c, and use lsof to see which fds are referenced 
in the read and write calls.


-- 
error compiling committee.c: too many arguments to function