perf_counter: Increase mmap limit

In a default 'perf top' run the tool will create a counter for
each online CPU. With enough CPUs this will eventually exhaust
the default limit.

So scale it up with the number of online CPUs.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index cb4062559b47..6cdf8248eda2 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1704,6 +1704,12 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
         user_extra = nr_pages + 1;
         user_lock_limit = sysctl_perf_counter_mlock >> (PAGE_SHIFT - 10);
+
+        /*
+         * Increase the limit linearly with more CPUs:
+         */
+        user_lock_limit *= num_online_cpus();
+
         user_locked = atomic_long_read(&user->locked_vm) + user_extra;
 
         extra = 0;