linux-kernel - Re: [PATCH v6 04/10] libperf: Add evsel mmap support

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Date:   Fri, 12 Mar 2021 19:29:40 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ian Rogers <irogers@...gle.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Honnappa Nagarahalli <honnappa.nagarahalli@....com>,
        Zachary.Leaf@....com, Raphael Gault <raphael.gault@....com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 04/10] libperf: Add evsel mmap support

On Fri, Mar 12, 2021 at 07:34:39AM -0700, Rob Herring wrote:
> On Fri, Mar 12, 2021 at 6:59 AM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Wed, Mar 10, 2021 at 05:08:31PM -0700, Rob Herring wrote:
> >
> > SNIP
> >
> > > +
> > >  static int
> > >  sys_perf_event_open(struct perf_event_attr *attr,
> > >                   pid_t pid, int cpu, int group_fd,
> > > @@ -137,6 +147,8 @@ void perf_evsel__free_fd(struct perf_evsel *evsel)
> > >  {
> > >       xyarray__delete(evsel->fd);
> > >       evsel->fd = NULL;
> > > +     xyarray__delete(evsel->mmap);
> > > +     evsel->mmap = NULL;
> > >  }
> > >
> > >  void perf_evsel__close(struct perf_evsel *evsel)
> > > @@ -156,6 +168,45 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu)
> > >       perf_evsel__close_fd_cpu(evsel, cpu);
> > >  }
> > >
> > > +int perf_evsel__mmap(struct perf_evsel *evsel, int pages)
> > > +{
> > > +     int ret, cpu, thread;
> > > +     struct perf_mmap_param mp = {
> > > +             .prot = PROT_READ | PROT_WRITE,
> > > +             .mask = (pages * page_size) - 1,
> > > +     };
> >
> > I don't mind using evsel->fd for dimensions below,
> > but we need to check in here that it's defined,
> > that perf_evsel__open was called
> 
> Right, so I'll add this here:
> 
> if (evsel->fd == NULL)
>     return -EINVAL;
> 
> Note that struct evsel has dimensions in it, but they are only set in
> the evlist code. I couldn't tell if that was by design or mistake.

we do? we have the cpus and threads in perf_evsel no?
also you'd need perf_evsel not evsel, right?

> 
> BTW, I just noticed perf_evsel__open is leaking memory on most of its
> error paths.

nice.. let's fix it ;-)

thanks,
jirka

> 
> >
> > jirka
> >
> > > +
> > > +     if (evsel->mmap == NULL &&
> > > +         perf_evsel__alloc_mmap(evsel, xyarray__max_x(evsel->fd), xyarray__max_y(evsel->fd)) < 0)
> > > +             return -ENOMEM;
> > > +
> > > +     for (cpu = 0; cpu < xyarray__max_x(evsel->fd); cpu++) {
> > > +             for (thread = 0; thread < xyarray__max_y(evsel->fd); thread++) {
> > > +                     int fd = FD(evsel, cpu, thread);
> > > +                     struct perf_mmap *map = MMAP(evsel, cpu, thread);
> > > +
> > > +                     if (fd < 0)
> > > +                             continue;
> > > +
> > > +                     perf_mmap__init(map, NULL, false, NULL);
> > > +
> > > +                     ret = perf_mmap__mmap(map, &mp, fd, cpu);
> > > +                     if (ret)
> > > +                             return -1;
> > > +             }
> > > +     }
> > > +
> > > +     return 0;
> > > +}
> > > +
> >
> > SNIP
> >
>