Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760843Ab3GSP5l (ORCPT ); Fri, 19 Jul 2013 11:57:41 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:52947 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760643Ab3GSP5k (ORCPT ); Fri, 19 Jul 2013 11:57:40 -0400 Date: Sat, 20 Jul 2013 00:57:27 +0900 Message-ID: <87ip064k60.wl%mitake.hitoshi@gmail.com> From: Hitoshi Mitake To: Andi Kleen Cc: acme@infradead.org, linux-kernel@vger.kernel.org, Andi Kleen , h.mitake@gmail.com, kirill.shutemov@linux.intel.com Subject: Re: [PATCH] perf, tools, bench: Fix memcpy benchmark for large sizes v2 In-Reply-To: <1374187398-14234-1-git-send-email-andi@firstfloor.org> References: <1374187398-14234-1-git-send-email-andi@firstfloor.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?ISO-2022-JP-2?B?R29qGyQoRCtXGyhC?=) APEL/10.8 Emacs/24.2 (x86_64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1523 Lines: 43 At Thu, 18 Jul 2013 15:43:18 -0700, Andi Kleen wrote: > > 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) In the latest mem-memcpy.c, this if (!src) is already fixed as if (!*src). This modification makes applying fail. Thanks, Hitoshi -- 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/