Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934611Ab3GRWn0 (ORCPT ); Thu, 18 Jul 2013 18:43:26 -0400 Received: from mga01.intel.com ([192.55.52.88]:22415 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933668Ab3GRWnW (ORCPT ); Thu, 18 Jul 2013 18:43:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.89,697,1367996400"; d="scan'208";a="372640283" From: Andi Kleen To: acme@infradead.org Cc: linux-kernel@vger.kernel.org, Andi Kleen , h.mitake@gmail.com, kirill.shutemov@linux.intel.com Subject: [PATCH] perf, tools, bench: Fix memcpy benchmark for large sizes v2 Date: Thu, 18 Jul 2013 15:43:18 -0700 Message-Id: <1374187398-14234-1-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.8.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 43 From: Andi Kleen glibc calloc() has an optimization to not explicitely memset() very large calloc allocations that just came from mmap(), because they are known to be zero. This could result in the perf memcpy benchmark reading only from the zero page, which gives unrealistic results. Always call memset explicitly on the source area to avoid this problem. Cc: h.mitake@gmail.com Cc: kirill.shutemov@linux.intel.com v2: Actually memset the right area and also fix the NULL check before. Signed-off-by: Andi Kleen --- tools/perf/bench/mem-memcpy.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/perf/bench/mem-memcpy.c b/tools/perf/bench/mem-memcpy.c index 93c83e3..0887b46 100644 --- a/tools/perf/bench/mem-memcpy.c +++ b/tools/perf/bench/mem-memcpy.c @@ -115,8 +115,10 @@ static void alloc_mem(void **dst, void **src, size_t length) die("memory allocation failed - maybe length is too large?\n"); *src = zalloc(length); - if (!src) + if (!*src) die("memory allocation failed - maybe length is too large?\n"); + /* Make sure to always replace the zero pages even if MMAP_THRESH is crossed */ + memset(*src, 0, length); } static u64 do_memcpy_cycle(memcpy_t fn, size_t len, bool prefault) -- 1.8.1.4 -- 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/