linux-kernel - Re: [PATCH v2 06/15] perf session: load data directory into tool process memory

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Date:   Thu, 29 Oct 2020 20:00:54 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 06/15] perf session: load data directory into tool
 process memory

Hi Jiri,

On Thu, Oct 29, 2020 at 12:40 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Wed, Oct 28, 2020 at 04:22:49PM +0900, Namhyung Kim wrote:
> > On Tue, Oct 27, 2020 at 11:43 PM Alexey Budankov
> > <alexey.budankov@...ux.intel.com> wrote:
> > >
> > >
> > > On 27.10.2020 15:21, Jiri Olsa wrote:
> > > > On Tue, Oct 27, 2020 at 10:37:58AM +0300, Alexey Budankov wrote:
> > > >> I agree perf report OOM issue can exist on really-big servers but data
> > > >> directories support for report mode for not-so-big servers and desktops
> > > >> is already enabled with this smaller change. Also really-big-servers
> > > >> come with really-big amount of memory and collection could possibly be
> > > >> limited to only interesting phases of execution so the issue could likely
> > > >> be avoided. At the same time threaded trace streaming could clarify on
> > > >> real use cases that are blocked by perf report OOM issue and that would
> > > >> clarify on exact required solution. So perf report OOM issue shouldn't
> > > >> be the showstopper for upstream of threaded trace streaming.
> > > >
> > > > so the short answer is no, right? ;-)
> > >
> > > Answer to what question? Resolve OOM in perf report for data directories?
> > > I don't see a simple solution for that. The next issue after OOM is resolved
> > > is a very long processing of data directories. And again there is no simple
> > > solution for that as well. But it still need progress in order to be resolved
> > > eventually.
> >
> > I think we should find a better way than just adding all events to the
> > ordered events queue in memory then processing them one by one.
> >
> > Separating tracking events (FORK/MMAP/...) might be the first step.
>
> I recall seeing this change before for threaded perf report,
> maybe even from you, right? ;-)

Yes, I did it a couple of years ago.  The last version is here:

https://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git/log/?h=perf/threaded-v5

Thanks
Namhyung