From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753114Ab1LSNk2 (ORCPT ); Mon, 19 Dec 2011 08:40:28 -0500 Received: from acsinet15.oracle.com ([141.146.126.227]:24401 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753043Ab1LSNkV (ORCPT ); Mon, 19 Dec 2011 08:40:21 -0500 From: Nelson Elhage To: Peter Zijlstra Cc: Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Nelson Elhage Subject: [PATCH 3/3] perf: builtin-record: Document and check that mmap_pages must be a power of two. Date: Mon, 19 Dec 2011 08:39:32 -0500 Message-Id: <1324301972-22740-4-git-send-email-nelhage@nelhage.com> X-Mailer: git-send-email 1.7.4.41.g50b8f In-Reply-To: <1324301972-22740-1-git-send-email-nelhage@nelhage.com> References: <1324301972-22740-1-git-send-email-nelhage@nelhage.com> X-Source-IP: acsinet21.oracle.com [141.146.126.237] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090203.4EEF3EA8.00D0,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that we automatically point users at it, let's provide them some guidance so that they hopefully don't just get mysterious EINVAL's from the kernel. Signed-off-by: Nelson Elhage --- tools/perf/Documentation/perf-record.txt | 2 +- tools/perf/builtin-record.c | 3 +++ tools/perf/util/util.h | 11 +++++++++++ 3 files changed, 15 insertions(+), 1 deletions(-) diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt index 5a520f8..2937f7e 100644 --- a/tools/perf/Documentation/perf-record.txt +++ b/tools/perf/Documentation/perf-record.txt @@ -89,7 +89,7 @@ OPTIONS -m:: --mmap-pages=:: - Number of mmap data pages. + Number of mmap data pages. Must be a power of two. -g:: --call-graph:: diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 45b23c1..275c78d 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -560,6 +560,9 @@ static int __cmd_record(int argc, const char **argv) if (mmap_pages == UINT_MAX) mmap_pages = (512 * 1024) / page_size; + if (!is_power_of_2(mmap_pages)) + die("--mmap_pages/-m value must be a power of two."); + if (forks) { child_pid = fork(); if (child_pid < 0) { diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h index 0128906..37be34d 100644 --- a/tools/perf/util/util.h +++ b/tools/perf/util/util.h @@ -245,4 +245,15 @@ int readn(int fd, void *buf, size_t size); #define _STR(x) #x #define STR(x) _STR(x) +/* + * Determine whether some value is a power of two, where zero is + * *not* considered a power of two. + */ + +static inline __attribute__((const)) +bool is_power_of_2(unsigned long n) +{ + return (n != 0 && ((n & (n - 1)) == 0)); +} + #endif -- 1.7.4.41.g50b8f