No output data, only column headers

[ElijahLynn]

Hi Brendan,

I am a bit of a noob to low-level performance (might be missing something well known in the 6 person circle ;)). I was going through http://www.brendangregg.com/blog/2017-05-04/the-pmcs-of-ec2.html as a tutorial and when I run the script I just get the column headers, with no delay and a return code of 0.

I am on Ubuntu 14.04 and Linux 3.13.0-129-generic.

[lnyng]

Try this perf stat -e cycles -e cycles -e r4f2e -e r412e -e r00c4 -e r00c5 -e instructions -a -I 1000 It may print out "not supported"

[baruch]

I've had it happen when the perf tool is not installed or the arch doesn't support the needed counters.

[martinvonwittich]

I've also stumbled over this, and I think a proper error message might be helpful here. I quickly hacked together a PoC in tlbstat:

https://github.com/martinvonwittich/pmc-cloud-tools/commit/7bafcd45b8c275fd0cb6c708b342918bcad954fa

Now tlbstat will report the following errors on my machine:

martin@martin ~/pmc-cloud-tools % ./tlbstat 
ERROR: your perf(1) doesn't seem to support the following events:
  cycles
  dtlb_load_misses.walk_active
  dtlb_store_misses.walk_active
  itlb_misses.walk_active
  instructions
root permissions, a more recent kernel and/or direct hardware access might help.

martin@martin ~/pmc-cloud-tools % sudo ./tlbstat
[sudo] Passwort für martin: 
ERROR: your perf(1) doesn't seem to support the following events:
  dtlb_load_misses.walk_active
  dtlb_store_misses.walk_active
  itlb_misses.walk_active
A more recent kernel and/or direct hardware access might help.

I unfortunately haven't found a machine yet where the tools do work, so I can't really test anything besides the error handling :/

If this works properly, I could integrate it in all the scripts and submit a PR.