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    SubjectRe: [PATCH RFC V2 00/10] perf top optimization
    Em Mon, Sep 18, 2017 at 10:57:08AM +0200, Jiri Olsa escreveu:
    > On Sun, Sep 10, 2017 at 07:23:13PM -0700, kan.liang@intel.com wrote:
    > > From: Kan Liang <kan.liang@intel.com>
    > >
    > > The patch series intends to fix the severe performance issue in
    > > Knights Landing/Mill, when monitoring in heavy load system.
    > > perf top costs a few minutes to show the result, which is
    > > unacceptable.
    > > With the patch series applied, the latency will reduces to
    > > several seconds.
    > >
    > > machine__synthesize_threads and perf_top__mmap_read costs most of
    > > the perf top time (> 99%).
    >
    > looks like this patchset adds locking into code paths
    > used by other single threaded tools and that might
    > be bad for them as noted by Andi in here:
    >
    > https://marc.info/?l=linux-kernel&m=149031672928989&w=2
    >
    > he proposed solution and it was changed&posted by Arnaldo in here:
    >
    > https://marc.info/?l=linux-kernel&m=149132267410294&w=2
    >
    > but looks like it never got merged
    >
    > could you please add this or similar code before you add the
    > locking code/overhead in?

    I'm rehashing that patch and adding it on top of what is in my perf/core
    branch, will push soon, for now you can take a look at tmp.perf/core.

    - Arnaldo

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