Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932652Ab3GPNO6 (ORCPT ); Tue, 16 Jul 2013 09:14:58 -0400 Received: from mail-pb0-f41.google.com ([209.85.160.41]:39508 "EHLO mail-pb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932308Ab3GPNO5 (ORCPT ); Tue, 16 Jul 2013 09:14:57 -0400 Date: Tue, 16 Jul 2013 22:14:45 +0900 Message-ID: <87bo62sl2y.wl%mitake.hitoshi@gmail.com> From: Hitoshi Mitake To: "Kirill A. Shutemov" Cc: Andi Kleen , acme@infradead.org, linux-kernel@vger.kernel.org, Andi Kleen , h.mitake@gmail.com, kirill.shutemov@linux.jf.intel.com Subject: Re: [PATCH] perf, tools, bench: Fix memcpy benchmark for large sizes In-Reply-To: <20130716101100.C2A70E0090@blue.fi.intel.com> References: <1373675551-18684-1-git-send-email-andi@firstfloor.org> <20130716101100.C2A70E0090@blue.fi.intel.com> 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: 1682 Lines: 46 At Tue, 16 Jul 2013 13:11:00 +0300 (EEST), Kirill A. Shutemov wrote: > > 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 > > Signed-off-by: Andi Kleen > > --- > > 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 93c83e3..690f75f 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); > > It should be memset(*src, 0, length) instead. > > There's fix for wrong memory allocation fail check in v3.11-rc1. I couldn't catch it, thanks. The memset() should be fixed. 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/