From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ananyev, Konstantin" Subject: Re: rte_mbuf.next in 2nd cacheline Date: Mon, 15 Jun 2015 18:34:13 +0000 Message-ID: <2601191342CEEE43887BDE71AB97725836A0AA03@irsmsx105.ger.corp.intel.com> References: <20150615141258.GA580@bricha3-MOBL3> <557EE1A0.609@6wind.com> <2601191342CEEE43887BDE71AB97725836A0A8A8@irsmsx105.ger.corp.intel.com> <557EECFF.3090402@6wind.com> <20150615152346.GC580@bricha3-MOBL3> <2601191342CEEE43887BDE71AB97725836A0A8FB@irsmsx105.ger.corp.intel.com> <20150615153943.GD580@bricha3-MOBL3> <2601191342CEEE43887BDE71AB97725836A0A91C@irsmsx105.ger.corp.intel.com> <20150615160208.GE580@bricha3-MOBL3> <2601191342CEEE43887BDE71AB97725836A0A952@irsmsx105.ger.corp.intel.com> <20150615162259.GA384@bricha3-MOBL3> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "dev@dpdk.org" , "Damjan Marion \(damarion\)" To: "Richardson, Bruce" Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 12268C316 for ; Mon, 15 Jun 2015 20:34:33 +0200 (CEST) In-Reply-To: <20150615162259.GA384@bricha3-MOBL3> Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > -----Original Message----- > From: Richardson, Bruce > Sent: Monday, June 15, 2015 5:23 PM > To: Ananyev, Konstantin > Cc: Olivier MATZ; dev@dpdk.org; Damjan Marion (damarion) > Subject: Re: [dpdk-dev] rte_mbuf.next in 2nd cacheline >=20 > On Mon, Jun 15, 2015 at 05:10:44PM +0100, Ananyev, Konstantin wrote: > > > > > > > -----Original Message----- > > > From: Richardson, Bruce > > > Sent: Monday, June 15, 2015 5:02 PM > > > To: Ananyev, Konstantin > > > Cc: Olivier MATZ; dev@dpdk.org; Damjan Marion (damarion) > > > Subject: Re: [dpdk-dev] rte_mbuf.next in 2nd cacheline > > > > > > On Mon, Jun 15, 2015 at 04:59:55PM +0100, Ananyev, Konstantin wrote: > > > > > > > > > > > > > > > > As I can see, vector TX is the only one that calls __rte_pktmbuf_pr= efree_seg() directly. > > > > All others use rte_pktmbuf_free_seg(), that does ' m->next =3D NULL= ' anyway. > > > > For vector TX - yes, need to verify that it would not introduce a s= lowdown. > > > > Konstantin > > > > > > > > > > But if the function is only directly called from one place, and that = doesn't > > > have a problem, why would we bother making any change at all? > > > > > > For future usages? > > But sure, if you believe that we can safely remove 'm->next =3D NULL' a= t RX path, > > without any changes in the __rte_pktmbuf_prefree_seg() - > > that seems fine to me. > > Konstantin > > >=20 > If we find it's not safe, we can add in the change to __rte_pktmbuf_prefr= ee_seg > as you suggest. >=20 > One other question: based on this, do you think it's safe to also remove = the > assignment to NULL from the pktmbuf_alloc function? I suspect it should b= e safe, and > that should help any traffic-generator type applications that use that fu= nction > extensively. So it will be setup to NULL, either by: - mbuf constructor. - TX full-path free descriptors code. - upper layer code that uses 'next' pointer explicitly. ? I can't come-up with some breakage scenario off-hand. But that means that we have to should avoid resetting tx_offload in pktmbuf= _alloc() too, right? Otherwise there probably wouldn't be any real gain. Konstantin >=20 > /Bruce