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    Subjectperf complains losting events

    I find there is a comment about losting events:

    * The kernel collects the number of events it couldn't send in a stretch and
    * when possible sends this number in a PERF_RECORD_LOST event. The number of
    * such "chunks" of lost events is stored in .nr_events[PERF_EVENT_LOST] while
    * total_lost tells exactly how many events the kernel in fact lost, i.e. it is
    * the sum of all struct lost_event.lost fields reported.
    * The total_period is needed because by default auto-freq is used, so
    * multipling nr_events[PERF_EVENT_SAMPLE] by a frequency isn't possible to get
    * the total number of low level events, it is necessary to to sum all struct
    * sample_event.period and stash the result in total_period.

    So my question is, whether the losting of events is a problem?
    I have saw it many times:

    [root@hp-dl580g7-01 perf]# ./perf kmem record sleep 1
    [ perf record: Woken up 0 times to write data ]
    [ perf record: Captured and wrote 21.789 MB (~951977 samples)
    Processed 0 events and LOST 76148!

    Check IO/CPU overload!

    [root@hp-dl580g7-01 perf]# ./perf kmem stat
    Processed 0 events and LOST 76148!

    Check IO/CPU overload!

    Total bytes requested: 5725028
    Total bytes allocated: 6291512
    Total bytes wasted on internal fragmentation: 566484
    Internal fragmentation: 9.003941%
    Cross CPU allocations: 28/84295

    Han Pingtian
    Quality Engineer
    hpt @ #kernel-qe
    Red Hat, Inc
    Freedom ... courage ... Commitment ... ACCOUNTABILITY

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