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    SubjectRe: [PATCH 09/15] perf_counter tools: optionally scale counter values in perfstat mode

    * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

    > From: Paul Mackerras <paulus@samba.org>
    >
    > Impact: new functionality
    >
    > This adds add an option to the perfstat mode of kerneltop to scale
    > the reported counter values according to the fraction of time that
    > each counter gets to count. This is invoked with the -l option (I
    > used 'l' because s, c, a and e were all taken already.) This uses
    > the new PERF_RECORD_TOTAL_TIME_{ENABLED,RUNNING} read format
    > options.
    >
    > With this, we get output like this:
    >
    > $ ./perfstat -l -e 0:0,0:1,0:2,0:3,0:4,0:5 ./spin
    >
    > Performance counter stats for './spin':
    >
    > 4016072055 CPU cycles (events) (scaled from 66.53%)
    > 2005887318 instructions (events) (scaled from 66.53%)
    > 1762849 cache references (events) (scaled from 66.69%)
    > 165229 cache misses (events) (scaled from 66.85%)
    > 1001298009 branches (events) (scaled from 66.78%)
    > 41566 branch misses (events) (scaled from 66.61%)
    >
    > Wall-clock time elapsed: 2438.227446 msecs
    >
    > This also lets us detect when a counter is zero because the
    > counter never got to go on the CPU at all. In that case we print
    > <not counted> rather than 0.

    Nice! Shouldnt this be the default mode of output?

    I think we want to make users aware of the fact when output is
    sampled due to over-commit, rather than precise, agreed?

    Ingo


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