Commit-ID: 880f57318450dbead6a03f9e31a1468924d6dd88 Gitweb: http://git.kernel.org/tip/880f57318450dbead6a03f9e31a1468924d6dd88 Author: Frederic Weisbecker <fweisbec@xxxxxxxxx> AuthorDate: Wed, 23 Mar 2011 19:29:39 +0100 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Wed, 23 Mar 2011 20:57:04 +0100 perf: Better fit max unprivileged mlock pages for tools needs 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@xxxxxxxxxx> Reported-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Reported-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Acked-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Stephane Eranian <eranian@xxxxxxxxxx> Cc: Stable <stable@xxxxxxxxxx> LKML-Reference: <1300904979-5508-1-git-send-email-fweisbec@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- kernel/perf_event.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 0c71422..c75925c 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -145,7 +145,8 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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