Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933397Ab3GVUWx (ORCPT ); Mon, 22 Jul 2013 16:22:53 -0400 Received: from merlin.infradead.org ([205.233.59.134]:52072 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933339Ab3GVUWt (ORCPT ); Mon, 22 Jul 2013 16:22:49 -0400 From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Andi Kleen , Hitoshi Mitake , "Kirill A. Shutemov" , Arnaldo Carvalho de Melo Subject: [PATCH 03/11] perf bench: Fix memcpy benchmark for large sizes Date: Mon, 22 Jul 2013 17:22:31 -0300 Message-Id: <1374524559-9839-4-git-send-email-acme@infradead.org> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1374524559-9839-1-git-send-email-acme@infradead.org> References: <1374524559-9839-1-git-send-email-acme@infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by merlin.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1552 Lines: 41 From: Andi Kleen The glibc calloc() function 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. Signed-off-by: Andi Kleen Cc: Hitoshi Mitake Cc: Kirill A. Shutemov Link: http://lkml.kernel.org/n/tip-pzz2qrdq9eymxda0y8yxdn33@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/bench/mem-memcpy.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/perf/bench/mem-memcpy.c b/tools/perf/bench/mem-memcpy.c index 25fd3f1..8cdca43 100644 --- a/tools/perf/bench/mem-memcpy.c +++ b/tools/perf/bench/mem-memcpy.c @@ -117,6 +117,8 @@ static void alloc_mem(void **dst, void **src, size_t length) *src = zalloc(length); 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/