Re: perf on 2.6.38-rc4 wedges my box

[Jeff Moyer <jmoyer@redhat.com>]

David Ahern <dsahern@gmail.com> writes:

> Have you tried '-e cpu-clock' for S/W based profiling vs the default H/W
> profiling? Add -v to see if the fallback to S/W is happening now.

Thanks for the suggestion, David.  I tried:

# perf record -v ls
  Warning:  ... trying to fall back to cpu-clock-ticks

couldn't open /proc/-1/status
couldn't open /proc/-1/maps
[ls output]
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.008 MB perf.data (~363 samples) ]

If I explicitly set '-e cpu-clock', then the output is the same,
except that the warning is gone.  What's up with the /proc/-1/*?

Now, when running perf record -e cpu-clock on the aio-stress run,
unsurprisingly, I get the same result:

# perf record -e cpu-clock -v -- ./aio-stress -O -o 0 -r 4 -d 32 -b 16 /dev/sds
couldn't open /proc/-1/status
couldn't open /proc/-1/maps
adding stage write
starting with write
file size 1024MB, record size 4KB, depth 32, ios per iteration 8
max io_submit 16, buffer alignment set to 4KB
threads 1 files 1 contexts 1 context offset 2MB verification off
adding file /dev/sds thread 0

and there it sits.  In this case, however, I did not see the NOHZ
warnings on the console, and this time the machine is still responding
to ping, but nothing else.

Cheers,
Jeff