perf tools: Have the page size value available for all tools

Its such a common need that we might as well have a global with that
value.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-mwfqji9f17k5j81l1404dk3q@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 6d50eb0..d480d8a 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -440,6 +440,8 @@
 {
 	const char *cmd;
 
+	page_size = sysconf(_SC_PAGE_SIZE);
+
 	cmd = perf_extract_argv0_path(argv[0]);
 	if (!cmd)
 		cmd = "perf-help";