perf record: Increase mmap buffering default

I've run into mmap overruns with the current 16 pages default,
increase it to 128 pages.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/perf_counter/builtin-record.c

@@ -21,7 +21,7 @@ static int			event_count[MAX_COUNTERS];
 static int			fd[MAX_NR_CPUS][MAX_COUNTERS];
 static int			nr_cpus				= 0;
 static unsigned int		page_size;
-static unsigned int		mmap_pages			= 16;
+static unsigned int		mmap_pages			= 128;
 static int			output;
 static const char		*output_name			= "perf.data";
 static int			group				= 0;