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    SubjectRe: [PATCH] perf stat: fix cvs output format
    Speaking from the user's seat. An optional (not just empty) cgroup
    field is fine as long it consistently appears when requested with -G
    option. The problem with print_metric_csv() was that in the case of
    unsupported counters 2 additional empty fields in the output are
    completely unexpected and not documented anywhere.

    Andi, in the output example in your commit
    92a61f6412d3a09d6462252a522fa79c9290f405 stalled-cycles-backend event
    has counter run time field, counter run time percentage field, empty
    metric value, empty metric unit, and then 2 other empty fields. Are
    they expected? If yes, what are they and why other events, e.g.
    stalled-cycles-frontend, don't have them? Am I missing something here?

    On Tue, Mar 6, 2018 at 11:03 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
    > On Tue, Mar 6, 2018 at 9:53 AM, Andi Kleen <ak@linux.intel.com> wrote:
    >>> Here is the output from your own commit:
    >>>
    >>> 423470,,stalled-cycles-frontend,509102,100.00,65.69,frontend cycles idle
    >>> <not supported>,,stalled-cycles-backend,0,100.00,,,,
    >>>
    >>> so line 1 has 7 fields, line 2 has 9 fields, and this is expected?
    >>
    >> If you had metrics on line 1 it would be correct.
    >>
    >> So you just shifted it to break that case.
    >>
    >> If you always want to have the same number of fields
    >> you need to add two empty fields to the normal output
    >> when there are no metrics.
    >
    > The number of separators is the only way to learn the number
    > of fields, therefore it must be a fixed number.
    >
    > Yeah, it could be the other way that supported ones have less
    > separators than it should. If we look at print_metric_csv() alone,
    > it should produce a same number of separators for all cases,
    > otherwise hard to count.
    >
    > So I believe we need an additional patch, like the one attached,
    > to make it complete? Note, I only spot the cgroup field here.

    --
    Ilya Pronin

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