From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207Ab3LMIxo (ORCPT ); Fri, 13 Dec 2013 03:53:44 -0500 Received: from mga11.intel.com ([192.55.52.93]:54371 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750834Ab3LMIxl (ORCPT ); Fri, 13 Dec 2013 03:53:41 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,477,1384329600"; d="scan'208";a="449437419" From: Adrian Hunter To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Jiri Olsa , Mike Galbraith , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: [PATCH 1/2] perf tools: Fix next_pow2_l() Date: Fri, 13 Dec 2013 10:53:35 +0200 Message-Id: <1386924816-24402-2-git-send-email-adrian.hunter@intel.com> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: <1386924816-24402-1-git-send-email-adrian.hunter@intel.com> References: <1386924816-24402-1-git-send-email-adrian.hunter@intel.com> Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org My implementation of next_pow2_l() was incorrect. e.g. perf record -m4296015872 uname rounding mmap pages size to 17592186044416 bytes (4294967296 pages) Invalid argument for --mmap_pages/-m Notice that the next power-of-2 value 4294967296 is less than the option value 4296015872. Change to using __builtin_clzl() and prevent the shift being equal to the width of the operand. Also __builtin_clzl(x) is undefined if x is 0, so adjust the condition to preclude that possibility. Now: perf record -m4296015872 uname rounding mmap pages size to 35184372088832 bytes (8589934592 pages) Invalid argument for --mmap_pages/-m Signed-off-by: Adrian Hunter --- tools/perf/util/util.h | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h index a1eea3e..ae609fe 100644 --- a/tools/perf/util/util.h +++ b/tools/perf/util/util.h @@ -284,13 +284,14 @@ static inline unsigned next_pow2(unsigned x) static inline unsigned long next_pow2_l(unsigned long x) { -#if BITS_PER_LONG == 64 - if (x <= (1UL << 31)) - return next_pow2(x); - return (unsigned long)next_pow2(x >> 32) << 32; -#else - return next_pow2(x); -#endif + int leading_zeros; + + if (x < 2) + return 1; + leading_zeros = __builtin_clzl(x - 1); + if (!leading_zeros) + return 0; + return 1UL << (BITS_PER_LONG - leading_zeros); } size_t hex_width(u64 v); -- 1.7.11.7