From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id C5D517EB0 for ; Thu, 4 Dec 2014 17:32:28 +0100 (CET) Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP; 04 Dec 2014 08:22:24 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,516,1413270000"; d="scan'208";a="642422360" Received: from irsmsx106.ger.corp.intel.com ([163.33.3.31]) by fmsmga002.fm.intel.com with ESMTP; 04 Dec 2014 08:22:23 -0800 Received: from irsmsx105.ger.corp.intel.com ([169.254.7.144]) by IRSMSX106.ger.corp.intel.com ([169.254.8.18]) with mapi id 14.03.0195.001; Thu, 4 Dec 2014 16:22:23 +0000 From: "Ananyev, Konstantin" To: Jean-Mickael Guerin , "Richardson, Bruce" Thread-Topic: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer template Thread-Index: AQHQD9VcFC/GuRQHHkC9L9QzYWax+5x/nOQA Date: Thu, 4 Dec 2014 16:22:22 +0000 Message-ID: <2601191342CEEE43887BDE71AB977258213BCB40@IRSMSX105.ger.corp.intel.com> References: <1417703181-23093-1-git-send-email-jean-mickael.guerin@6wind.com> <1417703181-23093-2-git-send-email-jean-mickael.guerin@6wind.com> <20141204143930.GA9300@bricha3-MOBL3> <2601191342CEEE43887BDE71AB977258213BCA09@IRSMSX105.ger.corp.intel.com> <54807A91.7050805@6wind.com> In-Reply-To: <54807A91.7050805@6wind.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.180] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer template X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Dec 2014 16:32:29 -0000 > -----Original Message----- > From: Jean-Mickael Guerin [mailto:jean-mickael.guerin@6wind.com] > Sent: Thursday, December 04, 2014 3:15 PM > To: Ananyev, Konstantin; Richardson, Bruce > Cc: dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializer = template >=20 > On 04/12/2014 15:42, Ananyev, Konstantin wrote: > > > > > >> -----Original Message----- > >> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson > >> Sent: Thursday, December 04, 2014 2:40 PM > >> To: Jean-Mickael Guerin > >> Cc: dev@dpdk.org > >> Subject: Re: [dpdk-dev] [PATCH 1/2] ixgbe: fix setup of mbuf initializ= er template > >> > >> On Thu, Dec 04, 2014 at 03:26:20PM +0100, Jean-Mickael Guerin wrote: > >>> Add a compiler barrier to make sure all fields covered by > >>> the marker rearm_data are assigned before the read. > >>> > >>> Signed-off-by: Jean-Mickael Guerin > >>> Acked-by: David Marchand > >>> Fixes: 0ff3324da2 ("ixgbe: rework vector pmd following mbuf changes") > >> > >> Acked-by: Bruce Richardson > >> > >>> --- > >>> lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 3 +++ > >>> 1 file changed, 3 insertions(+) > >>> > >>> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/librte_pmd_i= xgbe/ixgbe_rxtx_vec.c > >>> index 579bc46..c1b5a78 100644 > >>> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > >>> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > >>> @@ -739,6 +739,9 @@ ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq) > >>> mb_def.buf_len =3D rxq->mb_pool->elt_size - sizeof(struct rte_mbuf= ); > >>> mb_def.port =3D rxq->port_id; > >>> rte_mbuf_refcnt_set(&mb_def, 1); > >>> + > >>> + /* prevent compiler reordering: rearm_data covers previous fields *= / > >>> + rte_compiler_barrier(); > >>> rxq->mbuf_initializer =3D *((uint64_t *)&mb_def.rearm_data); > >>> return 0; > >>> } > >>> -- > > > > Hmm, can someone explain to me why do we need a compiler barrier here? > > Konstantin >=20 > rearm_data is a separate field and as well an array of length zero, > overlapping on purpose the fields data_off buf_len, port, refcnt. > It might depend on compiler, but I could see a wrong value of 0UL for > mbuf_initializer without the barrier (gcc 4.4.6). Ah ok then. Probably it is some sort of bug in old version of the gcc. >=20 >=20 > > > >>> 2.1.3 > >>>