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From: Ilya Maximets <i.maximets@samsung.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>,
	Thomas Monjalon <thomas.monjalon@6wind.com>
Cc: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
	bruce.richardson@intel.com, Dyasly Sergey <s.dyasly@samsung.com>,
	Jerin Jacob <jerin.jacob@caviumnetworks.com>,
	Jianbo Liu <jianbo.liu@linaro.org>,
	Tetsuya Mukawa <mukawa@igel.co.jp>
Subject: Re: [dpdk-dev] [PATCH RFC v3 0/3] Thread safe rte_vhost_enqueue_burst().
Date: Fri, 18 Mar 2016 12:55:17 +0300	[thread overview]
Message-ID: <56EBD085.4030500@samsung.com> (raw)
In-Reply-To: <20160318094642.GA23215@yliu-dev.sh.intel.com>



On 18.03.2016 12:46, Yuanhan Liu wrote:
> On Fri, Mar 18, 2016 at 10:34:56AM +0100, Thomas Monjalon wrote:
>> 2016-03-18 17:16, Yuanhan Liu:
>>> On Fri, Mar 18, 2016 at 09:09:04AM +0100, Thomas Monjalon wrote:
>>>> 2016-03-18 16:00, Yuanhan Liu:
>>>>> On Thu, Mar 17, 2016 at 04:29:32PM +0100, Thomas Monjalon wrote:
>>>>>> 2016-02-24 14:47, Ilya Maximets:
>>>>>>> Implementation of rte_vhost_enqueue_burst() based on lockless ring-buffer
>>>>>>> algorithm and contains almost all to be thread-safe, but it's not.
>>>>>>>
>>>>>>> This set adds required changes.
>>>>>>>
>>>>>>> First patch in set is a standalone patch that fixes many times discussed
>>>>>>> issue with barriers on different architectures.
>>>>>>>
>>>>>>> Second and third adds fixes to make rte_vhost_enqueue_burst thread safe.
>>>>>>
>>>>>> My understanding is that we do not want to pollute Rx/Tx with locks.
>>>>>>
>>>>>> Huawei, Yuanhan, Bruce, do you confirm?
>>>>>
>>>>> Huawei would like to do that, and I'm behind that. Let's do it.
>>>>
>>>> I'm not sure to understand. What do you want to do exactly?
>>>
>>> I was thinking we are on the same page :(
>>
>> Yes we are on the same page.
>> But it's better to make things explicit.
>>
>> There should be no lock in Rx/Tx drivers (including vhost).
>> The locking must be done by the caller (application level).
> 
> Yeah, that's why Huawei made the proposal and the patch.
> 
>> That's why this series "Thread safe rte_vhost_enqueue_burst" is rejected.

Hi all.
And what about first patch of this series:
"vhost: use SMP barriers instead of compiler ones." ?

It's not about thread safety in terms of 'lockless'. It is the standalone
patch that fixes many times discussed issue with barriers on arm.

Best regards, Ilya Maximets.

>>
>>> "do not want to pollute Rx/Tx with locks" == "remove lockless Rx/Tx, the
>>> proposal from Huawei", right?
>>>
>>> In another way, I'm behind the following patch from Huawei:
>>>
>>>     http://dpdk.org/dev/patchwork/patch/9740/
>>
>> The patch "vhost: remove lockless enqueue to the virtio ring" must me
>> reworked in 2 patches:
>> 1/ announce API change
> 
> That was my concern, and agreed we need that.
> 
>> 2/ remove locks
>>
>> Please avoid talking about removing "lockless" when actually removing locks.
> 
> Sorry, my bad.
> 
> 	--yliu
> 
> 

  reply	other threads:[~2016-03-18  9:55 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-24 11:47 Ilya Maximets
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 1/3] vhost: use SMP barriers instead of compiler ones Ilya Maximets
2016-03-18 10:08   ` Xie, Huawei
2016-03-18 10:23     ` Ilya Maximets
2016-03-18 10:27       ` Xie, Huawei
2016-03-18 10:39         ` Ilya Maximets
2016-03-18 10:47           ` Xie, Huawei
2016-03-18 11:00             ` Ilya Maximets
     [not found]               ` <C37D651A908B024F974696C65296B57B4C67825C@SHSMSX101.ccr.corp.intel.com>
     [not found]                 ` <56EBE9AE.9070400@samsung.com>
     [not found]                   ` <56EBF256.8040409@samsung.com>
2016-03-18 12:28                     ` Ilya Maximets
2016-03-18 12:23   ` [dpdk-dev] [PATCH v4] " Ilya Maximets
2016-03-18 12:41     ` Yuanhan Liu
2016-03-21  4:49       ` Ilya Maximets
2016-03-21 14:07         ` Ananyev, Konstantin
2016-03-21 17:25           ` Xie, Huawei
2016-03-21 17:36             ` Ananyev, Konstantin
2016-03-23 14:07     ` Xie, Huawei
2016-03-31 13:46       ` Thomas Monjalon
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 2/3] vhost: make buf vector for scatter RX local Ilya Maximets
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 3/3] vhost: avoid reordering of used->idx and last_used_idx updating Ilya Maximets
2016-03-17 15:29 ` [dpdk-dev] [PATCH RFC v3 0/3] Thread safe rte_vhost_enqueue_burst() Thomas Monjalon
2016-03-18  8:00   ` Yuanhan Liu
2016-03-18  8:09     ` Thomas Monjalon
2016-03-18  9:16       ` Yuanhan Liu
2016-03-18  9:34         ` Thomas Monjalon
2016-03-18  9:46           ` Yuanhan Liu
2016-03-18  9:55             ` Ilya Maximets [this message]
2016-03-18 10:10               ` Xie, Huawei
2016-03-18 10:24                 ` Thomas Monjalon

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