Messages in this thread | | | Date | Tue, 22 Sep 2020 20:32:49 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v3 05/10] libperf: Add libperf_evsel__mmap() |
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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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