From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-outbound-1.vmware.com (smtp-outbound-1.vmware.com [208.91.2.12]) by dpdk.org (Postfix) with ESMTP id B6EF17F1D for ; Wed, 29 Oct 2014 18:49:28 +0100 (CET) Received: from sc9-mailhost2.vmware.com (sc9-mailhost2.vmware.com [10.113.161.72]) by smtp-outbound-1.vmware.com (Postfix) with ESMTP id 36BA5280F7; Wed, 29 Oct 2014 10:58:12 -0700 (PDT) Received: from EX13-CAS-009.vmware.com (EX13-CAS-009.vmware.com [10.113.191.61]) by sc9-mailhost2.vmware.com (Postfix) with ESMTP id 2F984B1610; Wed, 29 Oct 2014 10:58:12 -0700 (PDT) Received: from EX13-MBX-026.vmware.com (10.113.191.46) by EX13-MBX-005.vmware.com (10.113.191.25) with Microsoft SMTP Server (TLS) id 15.0.775.38; Wed, 29 Oct 2014 10:58:00 -0700 Received: from EX13-MBX-026.vmware.com ([fe80::858b:7f42:fd7c:703d]) by EX13-MBX-026.vmware.com ([fe80::858b:7f42:fd7c:703d%17]) with mapi id 15.00.0775.031; Wed, 29 Oct 2014 10:57:59 -0700 From: Yong Wang To: Thomas Monjalon , Bruce Richardson Thread-Topic: [dpdk-dev] [PATCH 1/5] vmxnet3: Fix VLAN Rx stripping Thread-Index: AQHP5q+f3kqeQUkLF0OqkGkH2ZSdUZwuOPwAgAAiocWADkeWgIAJg64AgAEv4YCAAAo0AIAAFWcA Date: Wed, 29 Oct 2014 17:57:59 +0000 Message-ID: References: <1413181389-14887-1-git-send-email-yongwang@vmware.com> <20141029090449.GA8292@BRICHA3-MOBL> <1988013.IRBMoDeiJN@xps13> In-Reply-To: <1988013.IRBMoDeiJN@xps13> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.113.160.246] Content-Type: text/plain; charset="us-ascii" Content-ID: <32861E0D0DB92F49B35152D26AAC08A4@pa-exch1.vmware.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH 1/5] vmxnet3: Fix VLAN Rx stripping 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: Wed, 29 Oct 2014 17:49:29 -0000 Sounds good to me but it does look like the rte_rxmbuf_alloc() could use some comments to make it explicit that rte_pktmbuf_reset() is avoided by design for the reasons that Bruce described. Furthermore, rte_rxmbuf_alloc() is duplicated in almost all the pmd drivers. Will it make sense to promote it to a public API? Just a thought. Yong On 10/29/14, 2:41 AM, "Thomas Monjalon" wrote: >2014-10-29 09:04, Bruce Richardson: >> On Tue, Oct 28, 2014 at 09:57:14PM +0000, Yong Wang wrote: >> > On 10/22/14, 6:39 AM, "Stephen Hemminger" >> > wrote: >> >=20 >> >=20 >> > >On Mon, 13 Oct 2014 18:42:18 +0000 >> > >Yong Wang wrote: >> > > >> > >> Are you referring to the patch as a whole or your comment is about >>the >> > >>reset of vlan_tci on the "else" (no vlan tags stripped) path? I am >>not >> > >>sure I get your comments here. This patch simply fixes a bug on >>the rx >> > >>vlan stripping path (where valid vlan_tci stripped is overwritten >> > >>unconditionally later on the rx path in the original vmxnet3 pmd >> > >>driver). All the other pmd drivers are doing the same thing in >>terms of >> > >>translating descriptor status to rte_mbuf flags for vlan stripping. >> > > >> > >I was thinking that there are many fields in a pktmbuf and rather >>than >> > >individually >> > >setting them (like tci). The code should call the common >> > >rte_pktmbuf_reset before setting >> > >the fields. That way when someone adds a field to mbuf they don't >>have >> > >to chasing >> > >through every driver that does it's own initialization. >> >=20 >> > Currently rte_pktmbuf_reset() is used in rte_pktmbuf_alloc() but looks >> > like most pmd drivers use rte_rxmbuf_alloc() to replenish rx buffers, >> > which directly calls __rte_mbuf_raw_alloc >> > () without calling rte_pktmbuf_reset(). How about we change that in a >> > separate patch to all pmd drivers so that we can keep their behavior >> > consistent? >> >=20 >>=20 >> We can look to do that, but we need to beware of performance >>regressions if=20 >> we do so. Certainly the vector implementation of the ixgbe would be >>severely=20 >> impacted performance-wise if such a change were made. However, code >>paths=20 >> which are not as highly tuned, or which do not need to be as highly >>tuned=20 >> could perhaps use the standard function. >>=20 >> The main reason for this regression is that reset will clear all fields >>of=20 >> the mbuf, which would be wasted cycles for a number of the PMDs as they >>will=20 >> later set some of the fields based on values in the receive descriptor. >>=20 >> Basically, on descriptor rearm in a PMD, the only fields that need to >>be=20 >> reset would be those not set by the copy of data from the descriptor. > >This is typically a trade-off situation. >I think that we should prefer the performance. > >--=20 >Thomas