• Andi Kleen's avatar
    perf stat: Basic support for TopDown in perf stat · 44b1e60a
    Andi Kleen authored
    Add basic plumbing for TopDown in perf stat
    
    TopDown is intended to replace the frontend cycles idle/ backend cycles
    idle metrics in standard perf stat output.  These metrics are not
    reliable in many workloads, due to out of order effects.
    
    This implements a new --topdown mode in perf stat (similar to
    --transaction) that measures the pipe line bottlenecks using
    standardized formulas. The measurement can be all done with 5 counters
    (one fixed counter)
    
    The result are four metrics:
    
    FrontendBound, BackendBound, BadSpeculation, Retiring
    
    that describe the CPU pipeline behavior on a high level.
    
    The full top down methology has many hierarchical metrics.  This
    implementation only supports level 1 which can be collected without
    multiplexing. A full implementation of top down on top of perf is
    available in pmu-tools toplev.  (http://github.com/andikleen/pmu-tools)
    
    The current version works on Intel Core CPUs starting with Sandy Bridge,
    and Atom CPUs starting with Silvermont.  In principle the generic
    metrics should be also implementable on other out of order CPUs.
    
    TopDown level 1 uses a set of abstracted metrics which are generic to
    out of order CPU cores (although some CPUs may not implement all of
    them):
    
      topdown-total-slots       Available slots in the pipeline
      topdown-slots-issued      Slots issued into the pipeline
      topdown-slots-retired     Slots successfully retired
      topdown-fetch-bubbles     Pipeline gaps in the frontend
      topdown-recovery-bubbles  Pipeline gaps during recovery
                                from misspeculation
    
    These metrics then allow to compute four useful metrics:
    
    FrontendBound, BackendBound, Retiring, BadSpeculation.
    
    Add a new --topdown options to enable events.  When --topdown is
    specified set up events for all topdown events supported by the kernel.
    Add topdown-* as a special case to the event parser, as is needed for
    all events containing -.
    
    The actual code to compute the metrics is in follow-on patches.
    
    v2: Use standard sysctl read function.
    v3: Move x86 specific code to arch/
    v4: Enable --metric-only implicitly for topdown.
    v5: Add --single-thread option to not force per core mode
    v6: Fix output order of topdown metrics
    v7: Allow combining with -d
    v8: Remove --single-thread again
    v9: Rename functions, adding arch_ and topdown_.
    v10: Expand man page and describe TopDown better
    Paste intro into commit description.
    Print error when malloc fails.
    Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
    Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
    Link: http://lkml.kernel.org/r/1464119559-17203-1-git-send-email-andi@firstfloor.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    44b1e60a
group.c 554 Bytes