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    SubjectRe: perf: regression -- missing /sys/devices/system/cpu/perf_events

    * Vince Weaver <vweaver1@eecs.utk.edu> wrote:

    > On Tue, 24 May 2011, Ingo Molnar wrote:
    > >
    > > So, what is wrong with the method Peter suggested: the presence of the perf
    > > syscall (it not returning -ENOSYS) is bona fide evidence that perf is
    > > available.
    >
    > it's just hard to do that from a shell script.

    Yeah.

    > also, running the perf syscall can be tricky if you have a new kernel but an
    > older set of header files that doesn't have the syscall number defined.

    I suspect you could add some quick band-aid like:

    #ifndef __NR_perf_event_open
    # ifdef __i386__
    # define __NR_perf_event_open 336
    # endif
    # ifdef __x86_64__
    # define __NR_perf_event_open 298
    # endif
    # ifdef __powerpc__
    # define __NR_perf_event_open 319
    # endif
    # ifdef __arm__
    # define __NR_perf_event_open 364
    # endif
    #endif

    #ifndef __NR_perf_event_open
    # error Please add the __NR_perf_event_open definition for this architecture!
    #endif

    This should cover 99% of the users - and fill in the table as people report
    build failures :)

    Thanks,

    Ingo


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