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    SubjectRe: [PATCH] perf tools: fix guest mode monitoring on AMD
    On 2/27/12 10:52 AM, Stephane Eranian wrote:
    > On Mon, Feb 27, 2012 at 6:47 PM, David Ahern<dsahern@gmail.com> wrote:
    >> On 2/27/12 10:33 AM, Stephane Eranian wrote:
    >>>
    >>> Commit:
    >>>
    >>> 1aed267 perf kvm: Do guest-only counting by default
    >>>
    >>> introduced a bug on AMD systems whereby simple commands:
    >>>
    >>> $ perf stat ls
    >>> Performance counter stats for 'ls':
    >>> 0 cycles # 0.000 GHz
    >>> 0.003704596 seconds time elapsed
    >>>
    >>> would not count anything anymore. Same results for perf record.
    >>>
    >>> I tracked it down to guest mode exclusion being enabled
    >>> by default leading to attr->exclude_guest = 1. When
    >>> not operating under any sort of virtualization, this
    >>> causes the PMU not to count anything.
    >>>
    >>> The fix disables guest exclusion by default.
    >>>
    >>> Signed-off-by: Stephane Eranian<eranian@google.com>
    >>> ---
    >>>
    >>> diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
    >>> index 8109a90..c1017b3 100644
    >>> --- a/tools/perf/util/util.c
    >>> +++ b/tools/perf/util/util.c
    >>> @@ -6,7 +6,7 @@
    >>> * XXX We need to find a better place for these things...
    >>> */
    >>> bool perf_host = true;
    >>> -bool perf_guest = false;
    >>> +bool perf_guest = true;
    >>
    >>
    >> This was recently reverted to false by
    >> c4a7dca92bbb9881a5d678720f1d0c2153499749
    >>
    >> See: https://lkml.org/lkml/2012/2/8/234
    >>
    > Yeah, but that causes simple commands such as "perf stat -e cycles ls"
    > to return 0 count.
    >
    > So either you get a segfault or you get zero count. There is something
    > else going on here...

    agreed. Did you try reverting exclude_guest by default?



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