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SubjectRe: [PATCH 6/6] perf, sort: Allow unique sorting instead of combining hist_entries
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Hi Don,

On Wed, 9 Apr 2014 09:57:06 -0400, Don Zickus wrote:
> On Wed, Apr 09, 2014 at 02:31:00PM +0900, Namhyung Kim wrote:
>> On Mon, 24 Mar 2014 15:34:36 -0400, Don Zickus wrote:
>> > The cache contention tools needs to keep all the perf records unique in order
>> > to properly parse all the data. Currently add_hist_entry() will combine
>> > the duplicate record and add the weight/period to the existing record.
>> >
>> > This throws away the unique data the cache contention tool needs (mainly
>> > the data source). Create a flag to force the records to stay unique.
>>
>> No. This is why I said you need to add 'mem' and 'snoop' sort keys into
>> the c2c tool. This is not how sort works IMHO - if you need to make
>> samples unique let the sort key(s) distinguish them somehow, or you can
>> combine same samples (in terms of sort kes) and use the combined entry's
>> stat.nr_events and stat.period or weight.
>
> Ok. I understand your point. Perhaps this was my lack of fully
> understanding the sorting algorithm when I did this. I can look into
> adding the 'mem' and 'snoop'.
>
> One concern I do have is we were caculating statistics based on the weight
> (mean, median, stddev). I was afraid that combining the entries would
> throw off our calculations as we could no longer accurately determine them
> any more. Is that true?

Yes, if you want to calculate the stats accurately, it needs to be done
when processing samples not hist_entries IMHO.

Thanks,
Namhyung


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