Messages in this thread | | | Subject | Re: [PATCH v1 1/4] perf annotate: create a new hists to manage multiple events samples | From | "Jin, Yao" <> | Date | Mon, 11 Sep 2017 09:33:53 +0800 |
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On 9/8/2017 9:43 PM, Arnaldo Carvalho de Melo wrote: > Em Wed, Aug 16, 2017 at 06:18:33PM +0800, Jin Yao escreveu: >> An issue is found during using perf annotate. >> >> perf record -e cycles,branches ... >> perf annotate main --stdio >> >> The result only shows cycles. It should show both cycles and >> branches on the left side. It works with "--group", but need >> this to work even without groups. >> >> In current design, the hists is per event. So we need a new >> hists to manage the samples for multiple events and use a new >> hist_event data structure to save the map/symbol information >> for per event. > Humm, why do we need another hists? Don't we have one per evsel, don't > we have a evlist from where to get all of those evsels, can't we just > use that to add one column per evsel? > > - Arnaldo > >
Hi Arnaldo,
I'm considering a case.
Suppose we sample 2 events ("branches" and "cache-misses"). The samples of "branches" are hit in function A and the samples of "cache-misses" are hit in function B.
The branches evsel has one hists and cache-misses evsel has another hists.
The hists of branches evsel has one hist-entry which stands for the function A symbol. The hists of cache-misses evsel has one hist-entry which stands for the function B symbol.
If we start to show the instructions in function B from cache-misses evsel, we will lose the function A.
Because even if we get the branches evsel from the link in cache-misses evsel, but the function A is before function B and function B has been displayed yet, so the function A is lost.
Considering the number of events can be greater than 2, the code will be much more complicated. So using a global hists should be an easy solution.
Thanks Jin Yao
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