From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>,
Bernard Iremonger <bernard.iremonger@intel.com>,
Bruce Richardson <bruce.richardson@intel.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
Declan Doherty <declan.doherty@intel.com>
Cc: DPDK <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v3 3/4] bonding: take queue spinlock in rx/tx burst functions
Date: Wed, 15 Feb 2017 18:01:45 +0000 [thread overview]
Message-ID: <d95e6d02-6564-0c49-3be1-d7f9db378ff3@intel.com> (raw)
In-Reply-To: <1632739.trvk2NaClS@xps13>
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_lib.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?
Thanks,
ferruh
next prev parent reply other threads:[~2017-02-15 18:01 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 [this message]
2017-02-16 9:13 ` Bruce Richardson
2017-02-16 11:39 ` Iremonger, Bernard
2017-02-20 11:15 ` Ferruh Yigit
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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