path: root/kernel
diff options
authorFrederic Weisbecker <fweisbec@gmail.com>2011-03-23 19:29:39 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-14 13:01:58 -0700
commit6c66673c8abb839c99b9692d02ec8032a11e67af (patch)
tree2e2c0c6cee42b9ad5cd24c65a822f66baf9d7bf6 /kernel
parentc27b92295ab4c6b90b1cee94c4c9c1b4732e1c2e (diff)
perf: Better fit max unprivileged mlock pages for tools needs
commit 880f57318450dbead6a03f9e31a1468924d6dd88 upstream. The maximum kilobytes of locked memory that an unprivileged user can reserve is of 512 kB = 128 pages by default, scaled to the number of onlined CPUs, which fits well with the tools that use 128 data pages by default. However tools actually use 129 pages, because they need one more for the user control page. Thus the default mlock threshold is not sufficient for the default tools needs and we always end up to evaluate the constant mlock rlimit policy, which doesn't have this scaling with the number of online CPUs. Hence, on systems that have more than 16 CPUs, we overlap the rlimit threshold and fail to mmap: $ perf record ls Error: failed to mmap with 1 (Operation not permitted) Just increase the max unprivileged mlock threshold by one page so that it supports well perf tools even after 16 CPUs. Reported-by: Han Pingtian <phan@redhat.com> Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Stephane Eranian <eranian@google.com> LKML-Reference: <1300904979-5508-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index ad02feadb6b..f81f9d6395a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -62,7 +62,8 @@ static struct srcu_struct pmus_srcu;
int sysctl_perf_event_paranoid __read_mostly = 1;
-int sysctl_perf_event_mlock __read_mostly = 512; /* 'free' kb per user */
+/* Minimum for 128 pages + 1 for the user control page */
+int sysctl_perf_event_mlock __read_mostly = 516; /* 'free' kb per user */
* max perf event sample rate