Re: [perfmon2] about libpfm4 example:self_count.c

[stephane e. <er...@go...>]

The self-count example does not work. The support for remapped
counter does not quite work on X86. There is more than CR4 to
fix.

2011/11/18 explore_zjx <exp...@12...>:
> Hello,everyone!
>     I installed libpfm4 on my platform. The cpu is Q6600 and the OS is RHEL
> with 2.6.34 kernel.
>     I hit seg faults trying to run perf_examples/self_count.c in libpfm4,
> and all Google can find is that kernel support for user-level rdpmc was
> missing.
>     To enable the rdpmc instrction, I wrote a program to set the PCE bit of
> cr4.
>      Then I  recompiled the self_count.c example,it runs normally when I
> just monitor one event.
>       I means that I can only enable one event one time in the variable
> *gen_events.
>
> static const char *gen_events[]={
>         //"CPU_CLK_UNHALTED",
>         //"INST_RETIRED",
>         "MEM_LOAD_RETIRED:L2_MISS",
>         NULL
> };
>       Once I set up two events or more simultaneously, such as
> CPU_CLK_UNHALTED and MEM_LOAD_RETIRED:L2_MISS, the self_count can be
> executed, but the read result of  PMU counter is wrong.  The result of
> CPU_CLK_UNHALTED is always zero, while the other seems normal.
> So my question is that could I set up more events than one when I using
> rdpmc instruction.
>
>     I want to use rdpmc instruction because I want to reduce the overhead of
> read PMU as much as possible.  Would u like to give me another advice?
>    Thanks in advance!
>
> Jason
> 2011/11/18
>
>
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