perf evlist: Expose perf_event_mlock_kb_in_pages() helper

When the user doesn't set --mmap-pages, perf_evlist__mmap() will do it
by reading the maximum possible for a non-root user from the
/proc/sys/kernel/perf_event_mlock_kb file.

Expose that function so that 'perf trace' can, for root users, to bump
mmap-pages to a higher value for root, based on the contents of this
proc file.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-xay69plylwibpb3l4isrpl1k@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 4c9f510..6fb5725 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -986,26 +986,34 @@ out_unmap:
        return -1;
 }
 
-static size_t perf_evlist__mmap_size(unsigned long pages)
+unsigned long perf_event_mlock_kb_in_pages(void)
 {
-       if (pages == UINT_MAX) {
-               int max;
+       unsigned long pages;
+       int max;
 
-               if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
-                       /*
-                        * Pick a once upon a time good value, i.e. things look
-                        * strange since we can't read a sysctl value, but lets not
-                        * die yet...
-                        */
-                       max = 512;
-               } else {
-                       max -= (page_size / 1024);
-               }
+       if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
+               /*
+                * Pick a once upon a time good value, i.e. things look
+                * strange since we can't read a sysctl value, but lets not
+                * die yet...
+                */
+               max = 512;
+       } else {
+               max -= (page_size / 1024);
+       }
+
+       pages = (max * 1024) / page_size;
+       if (!is_power_of_2(pages))
+               pages = rounddown_pow_of_two(pages);
 
-               pages = (max * 1024) / page_size;
-               if (!is_power_of_2(pages))
-                       pages = rounddown_pow_of_two(pages);
-       } else if (!is_power_of_2(pages))
+       return pages;
+}
+
+static size_t perf_evlist__mmap_size(unsigned long pages)
+{
+       if (pages == UINT_MAX)
+               pages = perf_event_mlock_kb_in_pages();
+       else if (!is_power_of_2(pages))
                return 0;
 
        return (pages + 1) * page_size;

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index da46423..208897a 100644 (file)
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -158,6 +158,8 @@ int perf_evlist__parse_mmap_pages(const struct option *opt,
                                  const char *str,
                                  int unset);
 
+unsigned long perf_event_mlock_kb_in_pages(void);
+
 int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
                         bool overwrite, unsigned int auxtrace_pages,
                         bool auxtrace_overwrite);