Le 19 nov. 2016 21:29, "serge guelton" <sguel...@quarkslab.com> a écrit : > Thanks *a lot* victor for this great article. You not only very > accurately describe the method you used to track the performance bug, > but also give very convincing results.
You're welcome. I'm not 100% sure that adding the hot attrbute makes the performance of call_method reliable at 100%. My hope is that the 70% slowdown doesn't reoccur. > I still wonder what the conclusion should be: > > - (this) Micro benchmarks are not relevant at all, they are sensible to minor > factors that are not relevant to bigger applications Other benchmarks had peaks: logging_silent and json_loads. I'm unable to say if microbenchmarks must be used or not to cehck for performance regression or test the performance of a patch. So I try instead to analyze and fix performance issues. At least I can say that temporary peaks are higher and more frequent on microbenchmark. Homework: define what is a microbenchmark :-) > - There is a generally good code layout that favors most applications? This is an hard question. I don't know the answer. The hot attributes put tagged functions in a separated ELF section, but I understand that inside the section, order is not deterministic. Maybe the size of a function code matters too. What happens if a function grows? Does it impact other functions? > Maybe some core function from the interpreter ? I chose to only tag the most famous functions of the core right now. I'm testing tagging functions of extensions like json but I'm not sure that the result is significant. > Why does PGO fails to > ``find'' them? I don't use PGO on speed-python. I'm not sure that is PGO is reliable neither (reproductible performance). Victor
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