From: Ferruh Yigit <ferruh.yigit@intel.com>
To: "Iremonger, Bernard" <bernard.iremonger@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: Thomas Monjalon <thomas.monjalon@6wind.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"Doherty, Declan" <declan.doherty@intel.com>, DPDK <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx burst functions
Date: Mon, 20 Feb 2017 11:15:05 +0000 [thread overview]
Message-ID: <dadb2b64-f839-46f5-4a95-6cdeed414486@intel.com> (raw)
In-Reply-To: <8CEF83825BEC744B83065625E567D7C224D2A875@IRSMSX108.ger.corp.intel.com>
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.yigit@intel.com>
>> Cc: Thomas Monjalon <thomas.monjalon@6wind.com>; Iremonger, Bernard
>> <bernard.iremonger@intel.com>; Ananyev, Konstantin
>> <konstantin.ananyev@intel.com>; Doherty, Declan
>> <declan.doherty@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
next prev parent reply other threads:[~2017-02-20 11:15 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 15:14 [dpdk-dev] [PATCH 0/5] bonding: locks Bernard Iremonger
2016-05-05 15:14 ` [dpdk-dev] [PATCH 1/5] bonding: replace spinlock with read/write lock Bernard Iremonger
2016-05-05 17:12 ` Stephen Hemminger
2016-05-06 10:32 ` Declan Doherty
2016-05-06 15:55 ` Stephen Hemminger
2016-05-13 17:10 ` Ananyev, Konstantin
2016-05-13 17:18 ` Ananyev, Konstantin
2016-05-26 16:24 ` Iremonger, Bernard
2016-05-05 15:14 ` [dpdk-dev] [PATCH 2/5] bonding: add read/write lock to rx/tx burst functions Bernard Iremonger
2016-05-05 15:14 ` [dpdk-dev] [PATCH 3/5] bonding: remove memcopy of slaves from rx/tx burst function Bernard Iremonger
2016-05-05 15:14 ` [dpdk-dev] [PATCH 4/5] bonding: add read/write lock to stop function Bernard Iremonger
2016-05-05 15:15 ` [dpdk-dev] [PATCH 5/5] bonding: add read/write lock to the link_update function Bernard Iremonger
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 0/6] bonding: locks Bernard Iremonger
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 1/6] bonding: add spinlock to rx and tx queues Bernard Iremonger
2016-06-10 18:12 ` Ananyev, Konstantin
2016-06-12 17:11 ` [dpdk-dev] [PATCH v3 0/4] bonding: locks Bernard Iremonger
2016-06-12 17:11 ` [dpdk-dev] [PATCH v3 1/4] bonding: add spinlock to rx and tx queues Bernard Iremonger
2016-06-12 17:11 ` [dpdk-dev] [PATCH v3 2/4] bonding: grab queue spinlocks in slave add and remove Bernard Iremonger
2016-06-12 17:11 ` [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx burst functions Bernard Iremonger
2016-06-13 9:18 ` Bruce Richardson
2016-06-13 12:28 ` Iremonger, Bernard
2016-06-16 14:32 ` Bruce Richardson
2016-06-16 15:00 ` Thomas Monjalon
2016-06-16 16:41 ` Iremonger, Bernard
2016-06-16 18:38 ` Thomas Monjalon
2017-02-15 18:01 ` Ferruh Yigit
2017-02-16 9:13 ` Bruce Richardson
2017-02-16 11:39 ` Iremonger, Bernard
2017-02-20 11:15 ` Ferruh Yigit [this message]
2016-09-09 11:29 ` Ferruh Yigit
2016-06-12 17:11 ` [dpdk-dev] [PATCH v3 4/4] bonding: remove memcpy from " Bernard Iremonger
2016-09-11 12:39 ` Yuanhan Liu
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 2/6] bonding: grab queue spinlocks in slave add and remove Bernard Iremonger
2016-06-10 18:14 ` Ananyev, Konstantin
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 3/6] bonding: take queue spinlock in rx/tx burst functions Bernard Iremonger
2016-06-10 18:14 ` Ananyev, Konstantin
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 4/6] bonding: add spinlock to stop function Bernard Iremonger
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 5/6] bonding: add spinlock to link update function Bernard Iremonger
2016-05-26 16:38 ` [dpdk-dev] [PATCH v2 6/6] bonding: remove memcpy from burst functions Bernard Iremonger
2016-06-10 18:15 ` Ananyev, Konstantin
2016-06-10 14:45 ` [dpdk-dev] [PATCH v2 0/6] bonding: locks Bruce Richardson
2016-06-10 18:24 ` Iremonger, Bernard
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