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From: Jiri Olsa <jolsa@redhat.com>
To: Rob Herring <robh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Ian Rogers <irogers@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Raphael Gault <raphael.gault@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Namhyung Kim <namhyung@kernel.org>, Will Deacon <will@kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 05/10] libperf: Add libperf_evsel__mmap()
Date: Tue, 22 Sep 2020 20:32:49 +0200	[thread overview]
Message-ID: <20200922183249.GA2718767@krava> (raw)
In-Reply-To: <CAL_JsqJWGDwDa8bayjJ6L4hpwhekUKSngiynbyRw2WRWZeA8YA@mail.gmail.com>

On Tue, Sep 22, 2020 at 09:28:44AM -0600, Rob Herring wrote:
> On Fri, Sep 18, 2020 at 8:33 AM Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Fri, Sep 11, 2020 at 03:51:13PM -0600, Rob Herring wrote:
> > > In order to support usersapce access, an event must be mmapped. While
> > > there's already mmap support for evlist, the usecase is a bit different
> > > than the self monitoring with userspace access. So let's add a new
> > > perf_evsel__mmap() function to mmap an evsel. This allows implementing
> > > userspace access as a fastpath for perf_evsel__read().
> > >
> > > The mmapped address is returned by perf_evsel__mmap() primarily for
> > > users/tests to check if userspace access is enabled.
> > >
> > > Signed-off-by: Rob Herring <robh@kernel.org>
> > > ---
> > > v3:
> > >  - New patch split out from user access patch
> > > ---
> > >  tools/lib/perf/Documentation/libperf.txt |  1 +
> > >  tools/lib/perf/evsel.c                   | 31 ++++++++++++++++++++++++
> > >  tools/lib/perf/include/internal/evsel.h  |  2 ++
> > >  tools/lib/perf/include/perf/evsel.h      |  2 ++
> > >  tools/lib/perf/libperf.map               |  1 +
> > >  5 files changed, 37 insertions(+)
> > >
> > > diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
> > > index 0c74c30ed23a..0b4694ce42b9 100644
> > > --- a/tools/lib/perf/Documentation/libperf.txt
> > > +++ b/tools/lib/perf/Documentation/libperf.txt
> > > @@ -136,6 +136,7 @@ SYNOPSIS
> > >                         struct perf_thread_map *threads);
> > >    void perf_evsel__close(struct perf_evsel *evsel);
> > >    void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu);
> > > +  void *perf_evsel__mmap(struct perf_evsel *evsel, size_t length);
> > >    int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
> > >                         struct perf_counts_values *count);
> > >    int perf_evsel__enable(struct perf_evsel *evsel);
> > > diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> > > index 4dc06289f4c7..99fa53dc0887 100644
> > > --- a/tools/lib/perf/evsel.c
> > > +++ b/tools/lib/perf/evsel.c
> > > @@ -11,10 +11,12 @@
> > >  #include <stdlib.h>
> > >  #include <internal/xyarray.h>
> > >  #include <internal/cpumap.h>
> > > +#include <internal/mmap.h>
> > >  #include <internal/threadmap.h>
> > >  #include <internal/lib.h>
> > >  #include <linux/string.h>
> > >  #include <sys/ioctl.h>
> > > +#include <sys/mman.h>
> > >
> > >  void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr)
> > >  {
> > > @@ -156,6 +158,35 @@ void perf_evsel__close_cpu(struct perf_evsel *evsel, int cpu)
> > >       perf_evsel__close_fd_cpu(evsel, cpu);
> > >  }
> > >
> > > +void *perf_evsel__mmap(struct perf_evsel *evsel, size_t length)
> > > +{
> >
> > could you rather use 'int pages' insted of length as we
> > do in perf_evlist__mmap, so we keep the same interface
> >
> >   len = (pages + 1) * page_size
> 
> Sure, but what's the reason it is pages minus 1? It seems a bit odd to
> pass in 0 here to get 1 page which would be the typical usage.

the user mmap page is extra, so when you map 2 pages you actualy map 3,
but we want the size of what's available for storing events in the API

jirka


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  reply	other threads:[~2020-09-22 18:34 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-11 21:51 [PATCH v3 0/10] libperf and arm64 userspace counter access support Rob Herring
2020-09-11 21:51 ` [PATCH v3 01/10] arm64: pmu: Add hook to handle pmu-related undefined instructions Rob Herring
2020-09-28 18:26   ` Will Deacon
2020-09-29 13:46     ` Rob Herring
2020-09-29 17:49       ` Will Deacon
2020-09-29 20:46         ` Rob Herring
2020-09-11 21:51 ` [PATCH v3 02/10] arm64: pmu: Add function implementation to update event index in userpage Rob Herring
2020-09-11 21:51 ` [PATCH v3 03/10] arm64: perf: Enable pmu counter direct access for perf event on armv8 Rob Herring
2020-09-11 21:51 ` [PATCH v3 04/10] tools/include: Add an initial math64.h Rob Herring
2020-09-11 21:51 ` [PATCH v3 05/10] libperf: Add libperf_evsel__mmap() Rob Herring
2020-09-18 14:33   ` Jiri Olsa
2020-09-22 15:28     ` Rob Herring
2020-09-22 18:32       ` Jiri Olsa [this message]
2020-09-11 21:51 ` [PATCH v3 06/10] libperf: tests: Add support for verbose printing Rob Herring
2020-09-11 21:51 ` [PATCH v3 07/10] libperf: Add support for user space counter access Rob Herring
2020-09-11 21:51 ` [PATCH v3 08/10] libperf: Add arm64 support to perf_mmap__read_self() Rob Herring
2020-09-11 21:51 ` [PATCH v3 09/10] perf: arm64: Add test for userspace counter access on heterogeneous systems Rob Herring
2020-09-11 21:51 ` [PATCH v3 10/10] Documentation: arm64: Document PMU counters access from userspace Rob Herring
2020-09-12 20:53 ` [PATCH v3 0/10] libperf and arm64 userspace counter access support Jiri Olsa
2020-09-14 14:21   ` Rob Herring
     [not found]     ` <CANW9uytmafiNb_8oua9QY7L9O5BQTBFQBOMS3ZgjQ7aWj8CD2Q@mail.gmail.com>
2020-09-16  2:50       ` Rob Herring
2020-09-19  7:22         ` Itaru Kitayama
2020-09-22 15:23           ` Rob Herring

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