From f64186a734ac08b03842f785217ef5aa3ebdc559 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 23 Mar 2011 19:29:39 +0100 Subject: [PATCH] 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 Reported-by: Peter Zijlstra Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Frederic Weisbecker Acked-by: Arnaldo Carvalho de Melo Signed-off-by: Andi Kleen Cc: Stephane Eranian LKML-Reference: <1300904979-5508-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/perf_event.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index d1a6c04d8399..5f559b19c26a 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -58,7 +58,8 @@ static atomic_t nr_task_events __read_mostly; */ 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 -- 2.39.5