Messages in this thread | | | From | Song Liu <> | Subject | Re: [RFC 00/79] perf tools: Initial libperf separation | Date | Wed, 24 Jul 2019 08:49:18 +0000 |
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> On Jul 24, 2019, at 1:33 AM, Jiri Olsa <jolsa@redhat.com> wrote: > > On Wed, Jul 24, 2019 at 07:42:50AM +0000, Song Liu wrote: >> Hi Jiri, >> >>> On Jul 21, 2019, at 4:23 AM, Jiri Olsa <jolsa@kernel.org> wrote: >>> >>> hi, >>> 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 > > AFAICS some abstraction is needed to carry on the needed stuff > like mmaps, counts, group links, PMU details (type, cpus..) > >> 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. > > well, besides that we wanted to do this separation for tools/* sake, > I think that once libperf shares more interface on sampling and pmu > events parsing, it will be considerable choice also for out of the > tree tools
Yeah, in tree tools would benefit from it for sure. And they should also motivate out of the tree tools to use libperf.
> >>> >>> 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? > > yea, as I wrote in the perf_evsel__open patch changelog: > > It's a simplified version of evsel__open without fallback > stuff. We can try to merge it in the future to libperf, > but it has many glitches.
I was reading the code in your git tree and missed the change log.
Thanks for the explanations.
Song
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