On 2/16/2017 11:39 AM, Iremonger, Bernard wrote: > Hi Ferruh, > >> -----Original Message----- >> From: Richardson, Bruce >> Sent: Thursday, February 16, 2017 9:14 AM >> To: Yigit, Ferruh <ferruh.yi...@intel.com> >> Cc: Thomas Monjalon <thomas.monja...@6wind.com>; Iremonger, Bernard >> <bernard.iremon...@intel.com>; Ananyev, Konstantin >> <konstantin.anan...@intel.com>; Doherty, Declan >> <declan.dohe...@intel.com>; DPDK <dev@dpdk.org> >> Subject: Re: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx >> burst functions >> >> 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, >>>>> <snip> >>>>>> 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, there 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. >> >> /Bruce > > I am ok with option 2, provided they can be retrieved if needed.
Patches marked as rejected in patchwork. For future reference, patchwork ids: http://dpdk.org/dev/patchwork/patch/13482/ http://dpdk.org/dev/patchwork/patch/13483/ http://dpdk.org/dev/patchwork/patch/13484/ http://dpdk.org/dev/patchwork/patch/13485/ Thanks, ferruh
