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Date: Tue, 24 Oct 2017 13:47:55 +0200 From: Jiri Olsa <jolsa@...hat.com> To: Ingo Molnar <mingo@...nel.org> Cc: "Liang, Kan" <kan.liang@...el.com>, "acme@...nel.org" <acme@...nel.org>, "mingo@...hat.com" <mingo@...hat.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "peterz@...radead.org" <peterz@...radead.org>, "jolsa@...nel.org" <jolsa@...nel.org>, "wangnan0@...wei.com" <wangnan0@...wei.com>, "hekuang@...wei.com" <hekuang@...wei.com>, "namhyung@...nel.org" <namhyung@...nel.org>, "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>, "Hunter, Adrian" <adrian.hunter@...el.com>, "ak@...ux.intel.com" <ak@...ux.intel.com> Subject: Re: [PATCH V3 0/6] event synthesization multithreading for perf record On Tue, Oct 24, 2017 at 11:22:00AM +0200, Ingo Molnar wrote: > > * Liang, Kan <kan.liang@...el.com> wrote: > > > For 'all', do you mean the whole process? > > Yeah. > > > I think that's the ultimate goal. Eventually there will be per-CPU recording > > threads created at the beginning of perf record and go through the whole process. > > The plan is to do the multithreading step by step from the simplest case. > > Synthesizing stage is just a start. > > So, why not do it like the kernel did: add all the threads, create the percpu > files, and introduce a 'big perf lock' (big mutex) that is taken for all the > current non-threaded perf functionality. This should be fairly straightforward to > do and should be 'obviously correct'. > > _Then_ start doing the hard threading work on top of this, like threading the > synthesizing phase. > > Doing the whole per CPU thread setup/teardown for just the synthesizing part of it > looks like the wrong design. > > I.e. what I'm suggesting is no extra threading work, just organizing it in a > different fashion and increasing the life-time of the per CPU threads from 'perf > startup' to 'perf shutdown'. I recently made some changes on threaded record, which are based on Namhyungs time* API, which is needed to read/sort the data afterwards but I wasn't able to get any substantial and constant reduce of LOST events and then I got sidetracked and did not finish, but it's in here: git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git perf/data I'll try to rebase and send it out for comments jirka
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