Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757205Ab1CaIIH (ORCPT ); Thu, 31 Mar 2011 04:08:07 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:38402 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757164Ab1CaIHn (ORCPT ); Thu, 31 Mar 2011 04:07:43 -0400 Subject: Re: [PATCH 2/2] perf: Mmap 512 kiB by default From: Peter Zijlstra To: Frederic Weisbecker Cc: Arnaldo Carvalho de Melo , LKML , Ingo Molnar , Paul Mackerras , Stephane Eranian In-Reply-To: <1301535324-9735-1-git-send-email-fweisbec@gmail.com> References: <1301496028.4859.183.camel@twins> <1301535324-9735-1-git-send-email-fweisbec@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Thu, 31 Mar 2011 10:09:52 +0200 Message-ID: <1301558992.2250.489.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2332 Lines: 59 On Thu, 2011-03-31 at 03:35 +0200, Frederic Weisbecker wrote: > The default setting of perf record is to mmap 128 pages if the user > did not override with -m. > However the page size may vary accross different architecture > settings, giving different default size between each. > > Moreover the kernel side still has a default max number of mlocked > pages of 512 kiB + 1 page for unprivileged users. 128 + 1 pages > with page size > 4096 overlaps this threshold. > > Thus, better adapt to this limitation and set the default number of > pages to fit those 512 kiB + 1 page. > > Signed-off-by: Frederic Weisbecker > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Arnaldo Carvalho de Melo > Cc: Paul Mackerras > Cc: Stephane Eranian > --- > tools/perf/builtin-record.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > index 6febcc1..a7e14bd 100644 > --- a/tools/perf/builtin-record.c > +++ b/tools/perf/builtin-record.c > @@ -41,7 +41,7 @@ static u64 user_interval = ULLONG_MAX; > static u64 default_interval = 0; > > static unsigned int page_size; > -static unsigned int mmap_pages = 128; > +static unsigned int mmap_pages = UINT_MAX; > static unsigned int user_freq = UINT_MAX; > static int freq = 1000; > static int output; > @@ -506,6 +506,10 @@ static int __cmd_record(int argc, const char **argv) > if (have_tracepoints(&evsel_list->entries)) > perf_header__set_feat(&session->header, HEADER_TRACE_INFO); > > + /* 512 kiB: default amount of unprivileged mlocked memory */ > + if (mmap_pages == UINT_MAX) > + mmap_pages = (512 * 1024) / page_size; > + > if (forks) { > child_pid = fork(); > if (child_pid < 0) { Ok, these two patches look good, I'll queue them. However a follow up might be to change the perf-record parameter from nr_pages to kb, which is a much more user friendly interface anyway ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/