Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 28 Apr 2015 15:43:38 -0700 | Subject | Re: [RFC] x86, perf: Add an aperfmperf driver |
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On Tue, Apr 28, 2015 at 3:29 PM, Brown, Len <len.brown@intel.com> wrote: >> I think that turbostat could do some of its work without being >> root if we had a driver like this. > > Note that turbostat can be run as non-root this way: > > # setcap cap_sys_rawio=ep ./turbostat > # chmod +r /dev/cpu/*/msr > > For the debug case, there are a number of MSRs that turbostat must access, > so would still need permission for that case (which is the only case I use:-) >
True. This would only get the average turbo ratio. Of course, I think that can be done using cpu-cycles as well.
>> Thoughts? Would it make sense at all? Did I wire it up right? This is >> the only PMU driver I've ever written, and it could have any number of >> issues. > > APERF/MPERF, as with all per-thread MSRs, must be accessed > from the local processor. I didn't see where this driver > distinguishes the CPU. Also, I assume the intent is to return > a snapshot, rather than sampling, yes?
I think that the perf core takes care of that for us, but I'm not entirely sure.
--Andy
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