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 AFC7769C3 for ; Thu, 16 Feb 2017 12:39:15 +0100 (CET) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Feb 2017 03:39:12 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,169,1484035200"; d="scan'208";a="45920113" Received: from irsmsx106.ger.corp.intel.com ([163.33.3.31]) by orsmga002.jf.intel.com with ESMTP; 16 Feb 2017 03:39:11 -0800 Received: from irsmsx108.ger.corp.intel.com ([169.254.11.173]) by IRSMSX106.ger.corp.intel.com ([169.254.8.197]) with mapi id 14.03.0248.002; Thu, 16 Feb 2017 11:39:11 +0000 From: "Iremonger, Bernard" To: "Richardson, Bruce" , "Yigit, Ferruh" CC: Thomas Monjalon , "Ananyev, Konstantin" , "Doherty, Declan" , DPDK Thread-Topic: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx burst functions Thread-Index: AQHRxM18/A1UDGyp2k6AoPL2Wnlv+p/nDpiAgAAtvzCABOEFAIAAB/qAgAAnYdCAABVigIF/f2+AgAD+vQCAAChTIA== Date: Thu, 16 Feb 2017 11:39:09 +0000 Message-ID: <8CEF83825BEC744B83065625E567D7C224D2A875@IRSMSX108.ger.corp.intel.com> References: <1464280727-25752-2-git-send-email-bernard.iremonger@intel.com> <5839452.IzJ3v2K0cK@xps13> <8CEF83825BEC744B83065625E567D7C21A03A6D7@IRSMSX108.ger.corp.intel.com> <1632739.trvk2NaClS@xps13> <20170216091330.GC92400@bricha3-MOBL3.ger.corp.intel.com> In-Reply-To: <20170216091330.GC92400@bricha3-MOBL3.ger.corp.intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiYmZkMmYzOTMtMDI1MS00YjEwLWEwOTYtNzA0NWVhYjM2MWFhIiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE2LjIuMTEuMCIsIlRydXN0ZWRMYWJlbEhhc2giOiJGTjZGTElmVGo2NWh5XC9CTHRZMDhqWnZjNzFtZUpXb3hKVUVWVFJJM3pRTT0ifQ== x-ctpclassification: CTP_IC x-originating-ip: [163.33.239.182] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx burst functions X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Feb 2017 11:39:16 -0000 Hi Ferruh, > -----Original Message----- > From: Richardson, Bruce > Sent: Thursday, February 16, 2017 9:14 AM > To: Yigit, Ferruh > Cc: Thomas Monjalon ; Iremonger, Bernard > ; Ananyev, Konstantin > ; Doherty, Declan > ; DPDK > Subject: Re: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx= /tx > burst functions >=20 > On Wed, Feb 15, 2017 at 06:01:45PM +0000, Ferruh Yigit wrote: > > On 6/16/2016 7:38 PM, thomas.monjalon at 6wind.com (Thomas Monjalon) > wrote: > > > 2016-06-16 16:41, Iremonger, Bernard: > > >> Hi Thomas, > > >> > > >>> 2016-06-16 15:32, Bruce Richardson: > > >>>> On Mon, Jun 13, 2016 at 01:28:08PM +0100, Iremonger, Bernard > wrote: > > >>>>>> Why does this particular PMD need spinlocks when doing RX and > > >>>>>> TX, while other device types do not? How is adding/removing > > >>>>>> devices from a bonded device different to other control > > >>>>>> operations that can be done on physical PMDs? Is this not > > >>>>>> similar to say bringing down or hotplugging out a physical port > > >>>>>> just before an RX or TX > > >>> operation takes place? > > >>>>>> For all other PMDs we rely on the app to synchronise control > > >>>>>> and data plane operation - why not here? > > >>>>>> > > >>>>>> /Bruce > > >>>>> > > >>>>> This issue arose during VM live migration testing. > > >>>>> For VM live migration it is necessary (while traffic is running) > > >>>>> to be able to > > >>> remove a bonded slave device, stop it, close it and detach it. > > >>>>> It a slave device is removed from a bonded device while traffic > > >>>>> is running > > >>> a segmentation fault may occur in the rx/tx burst function. The > > >>> spinlock has been added to prevent this occurring. > > >>>>> > > >>>>> The bonding device already uses a spinlock to synchronise > > >>>>> between the > > >>> add and remove functionality and the > > >>> slave_link_status_change_monitor code. > > >>>>> > > >>>>> Previously testpmd did not allow, stop, close or detach of PMD > > >>>>> while traffic was running. Testpmd has been modified with the > > >>>>> following patchset > > >>>>> > > >>>>> http://dpdk.org/dev/patchwork/patch/13472/ > > >>>>> > > >>>>> It now allows stop, close and detach of a PMD provided in it is > > >>>>> not > > >>> forwarding and is not a slave of bonded PMD. > > >>>>> > > >>>> I will admit to not being fully convinced, but if nobody else has > > >>>> any serious objections, and since this patch has been reviewed > > >>>> and acked, I'm ok to merge it in. I'll do so shortly. > > >>> > > >>> Please hold on. > > >>> Seeing locks introduced in the Rx/Tx path is an alert. > > >>> We clearly need a design document to explain where locks can be > > >>> used and what are the responsibility of the control plane. > > >>> If everybody agrees in this document that DPDK can have some locks > > >>> in the fast path, then OK to merge it. > > >>> > > >>> So I would say NACK for 16.07 and maybe postpone to 16.11. > > >> > > >> Looking at the documentation for the bonding PMD. > > >> > > >> > http://dpdk.org/doc/guides/prog_guide/link_bonding_poll_mode_drv_li > > >> b.html > > >> > > >> In section 10.2 it states the following: > > >> > > >> Bonded devices support the dynamical addition and removal of slave > devices using the rte_eth_bond_slave_add / rte_eth_bond_slave_remove > APIs. > > >> > > >> If a slave device is added or removed while traffic is running, ther= e is the > possibility of a segmentation fault in the rx/tx burst functions. This is= most > likely to occur in the round robin bonding mode. > > >> > > >> This patch set fixes what appears to be a bug in the bonding PMD. > > > > > > It can be fixed by removing this statement in the doc. > > > > > > One of the design principle of DPDK is to avoid locks. > > > > > >> Performance measurements have been made with this patch set > applied and without the patches applied using 64 byte packets. > > >> > > >> With the patches applied the following drop in performance was > observed: > > >> > > >> % drop for fwd+io: 0.16% > > >> % drop for fwd+mac: 0.39% > > >> > > >> This patch set has been reviewed and ack'ed, so I think it should > > >> be applied in 16.07 > > > > > > I understand your point of view and I gave mine. > > > Now we need more opinions from others. > > > > > > > Hi, > > > > These patches are sitting in the patchwork for a long time. Discussion > > never concluded and patches kept deferred each release. > > > > I think we should give a decision about them: > > > > 1- We can merge them in this release, they are fixing a valid problem, > > and patches are already acked. > > > > 2- We can reject them, if not having them for more than six months not > > caused a problem, perhaps they are not really that required. And if > > somebody needs them in the future, we can resurrect them from > patchwork. > > > > I vote for option 2, any comments? > > > +1 on option 2. There are obviously not badly needed if nobody is asking > for them for over six months. >=20 > /Bruce I am ok with option 2, provided they can be retrieved if needed. Regards, Bernard.