From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 79A707EB0 for ; Thu, 4 Dec 2014 18:17:36 +0100 (CET) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga103.jf.intel.com with ESMTP; 04 Dec 2014 09:15:39 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,516,1413270000"; d="scan'208";a="618678113" Received: from irsmsx106.ger.corp.intel.com ([163.33.3.31]) by orsmga001.jf.intel.com with ESMTP; 04 Dec 2014 09:17:18 -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 17:17:17 +0000 From: "Ananyev, Konstantin" To: "Richardson, Bruce" Thread-Topic: [dpdk-dev] [PATCH 2/2] ixgbe: don't override mbuf buffer length Thread-Index: AQHQD85vrzKVJNav6E2ecmauZYfKoZx/gkeggAAIQACAAAIlgIAAByqAgAAAWwCAAAeAkIAAC9YAgAABbgA= Date: Thu, 4 Dec 2014 17:17:16 +0000 Message-ID: <2601191342CEEE43887BDE71AB977258213BCB91@IRSMSX105.ger.corp.intel.com> References: <1417703181-23093-1-git-send-email-jean-mickael.guerin@6wind.com> <20141204151500.GC9300@bricha3-MOBL3> <2601191342CEEE43887BDE71AB977258213BCA80@IRSMSX105.ger.corp.intel.com> <4349408.QROSJAq1DS@xps13> <2601191342CEEE43887BDE71AB977258213BCAE4@IRSMSX105.ger.corp.intel.com> <2601191342CEEE43887BDE71AB977258213BCB11@IRSMSX105.ger.corp.intel.com> <20141204165847.GA7732@bricha3-MOBL3> In-Reply-To: <20141204165847.GA7732@bricha3-MOBL3> 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 2/2] ixgbe: don't override mbuf buffer length 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 17:17:37 -0000 > -----Original Message----- > From: Richardson, Bruce > Sent: Thursday, December 04, 2014 4:59 PM > To: Ananyev, Konstantin > Cc: Thomas Monjalon; dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 2/2] ixgbe: don't override mbuf buffer len= gth >=20 > On Thu, Dec 04, 2014 at 04:18:03PM +0000, Ananyev, Konstantin wrote: > > > > > > > -----Original Message----- > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ananyev, Konstan= tin > > > Sent: Thursday, December 04, 2014 4:05 PM > > > To: Thomas Monjalon > > > Cc: dev@dpdk.org > > > Subject: Re: [dpdk-dev] [PATCH 2/2] ixgbe: don't override mbuf buffer= length > > > > > > > > > > > > > -----Original Message----- > > > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] > > > > Sent: Thursday, December 04, 2014 3:48 PM > > > > To: Ananyev, Konstantin > > > > Cc: dev@dpdk.org; Richardson, Bruce > > > > Subject: Re: [dpdk-dev] [PATCH 2/2] ixgbe: don't override mbuf buff= er length > > > > > > > > 2014-12-04 15:29, Ananyev, Konstantin: > > > > > From: Richardson, Bruce > > > > > > On Thu, Dec 04, 2014 at 02:50:11PM +0000, Ananyev, Konstantin w= rote: > > > > > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jean-Mic= kael Guerin > > > > > > > > The template mbuf_initializer is hard coded with a buflen w= hich > > > > > > > > might have been set differently by the application at the t= ime of > > > > > > > > mbuf pool creation. > > > > > > > > > > > > > > > > Switch to a mbuf allocation, to fetch the correct default v= alues. > > > > > > > > There is no performance impact because this is not a data-p= lane API. > > > > > > > > > > > > > > > > Signed-off-by: Jean-Mickael Guerin > > > > > > > > Acked-by: David Marchand > > > > > > > > Fixes: 0ff3324da2 ("ixgbe: rework vector pmd following mbuf= changes") > > > > > > > > --- > > > > > > > > lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 19 ++++++++++++---= ---- > > > > > > > > 1 file changed, 12 insertions(+), 7 deletions(-) > > > > > > > > > > > > > > > > diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c b/lib/li= brte_pmd_ixgbe/ixgbe_rxtx_vec.c > > > > > > > > index c1b5a78..f7b02f5 100644 > > > > > > > > --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > > > > > > > +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > > > > > > > @@ -732,17 +732,22 @@ static struct ixgbe_txq_ops vec_txq_o= ps =3D { > > > > > > > > int > > > > > > > > ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq) > > > > > > > > { > > > > > > > > - struct rte_mbuf mb_def =3D { .buf_addr =3D 0 }; /* zeroed= mbuf */ > > > > > > > > + struct rte_mbuf *mb_def; > > > > > > > > > > > > > > > > - mb_def.nb_segs =3D 1; > > > > > > > > - mb_def.data_off =3D RTE_PKTMBUF_HEADROOM; > > > > > > > > - 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); > > > > > > > > + mb_def =3D rte_pktmbuf_alloc(rxq->mb_pool); > > > > > > > > > > > > > > Could you explain to me, what is an advantage of using dynami= c allocation vs local struct here? > > > > > > > I don't see any. > > > > > > > > > > > > It means that we get an mbuf that is initialized as done by the= initialization > > > > > > function passed to the mempool_create call. The static variable= method assumes > > > > > > that we configure the mbuf using default setting for buf_len et= c. > > > > > > > > > > I understand that, but why it can't be done in some other way? > > > > > Without allocating/freeing? > > > > > Let say, at mempool_create() store obj_init() and then add abilit= y to call it again? > > > > > Anyway, it doesn't look to me like a critical problem, that requi= res an urgent patch for 1.8. > > > > > > > > Konstantin, when a bug is seen, it must be fixed ASAP. > > > > > > Well, it will be exposed only if someone will use a custom mbufs righ= t? > > > I.e, the se 2 lines would not be correct: > > > mb_def.data_off =3D RTE_PKTMBUF_HEADROOM; > > > mb_def.buf_len =3D rxq->mb_pool->elt_size - sizeof(struct rte_mbuf); > > > > > > Thoug we setup same data_off like that in all other PMDs as well. > > > Something like that: > > > m->data_off =3D RTE_PKTMBUF_HEADROOM; > > > could be seen across all RX functions we have for different PMDs. > > > > > > The only difference is buf_len, but in theory even with dynamic alloc= ation, > > > the fix would be totally correct. > > > As no one can guarantee, that with custom mbufs, all buffers inside t= he pool will have the same length. > > > > Which makes me think, that we probably shouldn't overwrite buf_len by r= xq->mbuf_initializer. > > > I believe that it is perfectly safe to do so. All buffers from a mempool = are meant > to be the same size, therefore reading the length of one buffer should te= ll you > what size all buffers are. Yes, objects in the mempool are the same size But nothing prevents you, in your custom obj_init() to setup mbuf->buf_len = to some other value, that could be smaller, then mempool element size. Let say you'd like all your mbufs from particular mempool to be at least 2K= long and 1K aligned. So you set RTE_MBUF_REFCNT_ATOMIC=3Dn, and call rte_mempool_create(...,els= t_size=3D0xc00,...); Then at you custom obj_init() you do: struct rte_mbuf *m =3D RTE_ALIGN_CEIL(_m, 1024); buf_len =3D mp->elt_size - sizeof(struct rte_mbuf) - (m - _m); ... >>From my point, nothing wrong is done here, and we have a mempool where mbuf= s might have different buf_len. Another example, is attachment of external buffer to the mbuf. We are doing it to support zero-copy inside our vhost app. Right now we don't allow external buffer length be bigger then mbuf buf_len= , but again some people may like to allow that. > If we do hit a scenario where we do need to support > variable size buffers from a single mempool, we can do that via the older= unoptimized > code paths, I think, since it's a definite edge case. >=20 > /Bruce