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    SubjectRe: [PATCH 12/18] perf ui/hist: Add support for event group view
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    On Mon, 3 Dec 2012 11:23:27 +0100, Jiri Olsa wrote:
    > On Mon, Dec 03, 2012 at 10:56:28AM +0900, Namhyung Kim wrote:
    >> On Fri, Nov 30, 2012 at 10:29 PM, Jiri Olsa <jolsa@redhat.com> wrote:
    >> > ok, so this is the part thats common for both multi diff and group
    >> > report and hugely depends on how we link matching hist_entry
    >> >
    >> > To sum to what group report does here:
    >> >
    >> > 1) starting with event group
    >> > 2) the function 'he' belongs to leader hists
    >> > 3) display leaders data value
    >> > 4) if 'symbol_conf.event_group' is enabled, we want to display all
    >> > group members data values in a column
    >> > 5) say we have group of 3 events 'e1,e2,e3' and e1 being the leader,
    >> > we have following possibilities:
    >> > - e1 have no pairs
    >> > - e1 is paired with e2
    >> > - e1 is paired with e3
    >> > - e1 is paired with e2 and e3 (e1 could also be dummy one)
    >> > 6) need to display 3 values wrt to e1,e2,e3 output order
    >> > 7) because events belongs to a group, each evsel carries group idx
    >> > 8) so we walk all pairs and compute the eX value and put it
    >> > into temporary array based on its group idx
    >> > 9) finally we display all temporary array values
    >> >
    >> >
    >> > To sum up what multi diff needs to do here:
    >> >
    >> > 1) starting with 3 separate matching events from different
    >> > evlists(sessions)
    >> > 2 - 5) are similar
    >> > 6) need to display single diff value of hist_entry that
    >> > belongs to evsel, that belongs to a column we are just
    >> > displaying value for
    >> > 7) events are not part of group; based on
    >> > [PATCH 02/14] perf tool: Add struct perf_hpp_fmt into hpp callbacks
    >> > we can tell what column we are in -> session -> evlist
    >> > 8) we need to walk all pairs and for each hist_entry:
    >> > - compare all evsels (from point 7 evlist)
    >> > and match hists pointer
    >> > - when found, we have a matching hist_entry for this column
    >> > 9) print out the value of matching hist_entry
    >> >
    >> >
    >> > I think both this processing could be simplified by having hist_entry
    >> > pairs connected via array and not linked list.
    >> >
    >> >
    >> > For group report, each leader hist_entry would have 'pairs' array
    >> > with the size of event group. Then we could omit the temporary array
    >> > creation by:
    >> > - walking the leaders pairs
    >> > - when pair is found -> compute data -> display
    >> > - when pair is NULL -> display 0
    >> >
    >> >
    >> > For multi diff, each baseline hist_entry would have 'pairs' array
    >> > with the size equal to number of data files on diff command input.
    >> > This way we could use the data from point 7 to directly access
    >> > related hist_entry.
    >> >
    >> >
    >> > ufff... thoughts? ;-)
    >>
    >> Nice summary, really! :)
    >>
    >> Yeah, I do think it's better to use array for this. If Arnaldo has no
    >> objection to this approach, I'll convert my code to use the array.
    >
    > we discussed with Arnaldo and decided to stay with current approach and
    > make the change later if needed.. to be able to see/meassure the benefit
    >
    > I made some initial attempt to workaround this and it appears to be
    > not that bad ;) I'll repost my changes shortly..

    Hmm.. so are you OK with this patch now?

    Thanks,
    Namhyung


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