Messages in this thread | | | Date | Tue, 15 Mar 2022 22:11:54 +0200 | Subject | Re: [PATCH] perf intel-pt: Synthesize cycle events | From | Adrian Hunter <> |
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On 15.3.2022 20.00, Steinar H. Gunderson wrote: > On Tue, Mar 15, 2022 at 01:32:38PM +0200, Adrian Hunter wrote: >>> I think the structure looks good, but I'm not sure about updating >>> e.g. ptq->last_cy_insn_cnt in both functions? Does that make sense? >> It should only be updated in the new intel_pt_synth_cycle_sample(). >> intel_pt_synth_instruction_sample() should be unchanged. > > Hm, OK. But something definitely changed between my original patch and > your change. (The first patch; I didn't try the last one yet.) With my > patch, I got (on a specific trace, synthing cycles only with perf report > --itrace=y0nse): > > Samples: 4M of event 'cycles:uH', Event count (approx.): 4844309 > > With yours on the same file: > > Samples: 2M of event 'cycles:uH', Event count (approx.): 77622449 > > The relative times between functions are also pretty different (although > none of them are obviously crazy), so one of them has to be wrong. > Is this to be expected, ie., would you expect your change to fix some > bad bug on cycle-only synth? For reference, “perf script --itrace=i0ns > -F +ipc | grep -c IPC:” (a quick proxy for the number of CYC packets :-) ) > yields 4836782, so I'm a bit surprised why there are only 2M events > being emitted from that.
Sorry, my first suggestion has issues, but the second is better.
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