Messages in this thread | | | Date | Wed, 17 Feb 2016 11:26:16 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 01/23] perf record: Add --all-user/--all-kernel options |
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Em Tue, Feb 16, 2016 at 07:10:37PM -0800, Andi Kleen escreveu: > > Need to investigate why there are kernel samples when --all-user is used and > > the other way around as well.
> This is a known issue due to skid. PEBS usually avoids it.
Right, thanks for pointing this out, we have to detect that :p is not being used and warn the user about this possibility, i.e. user asks for just kernel samples, tool finds user samples, tell that using :p+ may help.
Now, using plain:
# perf record --all-user -a sleep 2
will make it use the default which is 'cycles' with the highest precision available on the machine, and that leaves just a few samples that supposedly have the MISC_KERNEL bit set in the perf_event_attr header, those are not mapping to any mmap area known to the tool, I'm investigating what this is.
I'll apply the patch as-is, we'll check later OPT_ magic to tell that those options are mutually exclusive.
- Arnaldo
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