Messages in this thread | | | From | Song Liu <> | Subject | Re: [RFC 00/79] perf tools: Initial libperf separation | Date | Thu, 25 Jul 2019 05:23:17 +0000 |
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> On Jul 24, 2019, at 6:50 AM, Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote: > > Em Wed, Jul 24, 2019 at 07:42:50AM +0000, Song Liu escreveu: >>> On Jul 21, 2019, at 4:23 AM, Jiri Olsa <jolsa@kernel.org> wrote: > >>> we have long term goal to separate some of the perf functionality >>> into library. This patchset is initial effort on separating some >>> of the interface. > >>> Currently only the basic counting interface is exported, it allows >>> to: >>> - create cpu/threads maps >>> - create evlist/evsel objects >>> - add evsel objects into evlist >>> - open/close evlist/evsel objects >>> - enable/disable events >>> - read evsel counts > >> Based on my understanding, evsel and evlist are abstractions in >> perf utilities. I think most other tools that use perf UAPIs are >> not built based on these abstractions. I looked at a few internal >> tools. Most of them just uses sys_perf_event_open() and struct >> perf_event_attr. I am not sure whether these tools would adopt >> libperf, as libperf changes their existing concepts/abstractions. > > Right, and for now we're just trying to have something that is not so > tied to perf and could possibly be useful outside tools/perf/ when the > need arises for whatever new tool or pre-existing one. > > There are features there that may be interesting to use outside perf, > time will tell.
Thanks for the explanation. This is not an easy task. :)
> >>> The initial effort was to have total separation of the objects >>> from perf code, but it showed not to be a good way. The amount >>> of changed code was too big with high chance for regressions, >>> mainly because of the code embedding one of the above objects >>> statically. > >>> We took the other approach of sharing the objects/struct details >>> within the perf and libperf code. This way we can keep perf >>> functionality without any major changes and the libperf users >>> are still separated from the object/struct details. We can move >>> to total libperf's objects separation gradually in future. > >> I found some duplicated logic between libperf and perf, for >> example, perf_evlist__open() and evlist__open(). Do we plan to >> merge them in the future? > > He is just slowly moving things to a public libperf while keeping perf > working, in the end the goal is to have as much stuff that is not > super specific to some of the existing perf tools > (tools/perf/builtin-*.c) in libperf as possible. > > It is still early in this effort, that is why he is still leaving it in > tools/perf/lib/ and not in tools/lib/perf/ :-)
I saw that discussion. It is a good strategy.
Thanks, Song
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