[dpdk-dev] [PATCH v3 1/8] eal: introduce DMA memory barriers

Yongseok Koh yskoh at mellanox.com
Thu Jan 25 20:08:22 CET 2018


> On Jan 22, 2018, at 8:35 PM, Jerin Jacob <jerin.jacob at caviumnetworks.com> wrote:
> 
> -----Original Message-----
>> Date: Mon, 22 Jan 2018 18:29:31 +0000
>> From: Yongseok Koh <yskoh at mellanox.com>
>> To: Andrew Rybchenko <arybchenko at solarflare.com>, Thomas Monjalon
>> <thomas at monjalon.net>, "jianbo.liu at arm.com" <jianbo.liu at arm.com>, Jerin
>> Jacob <jerin.jacob at caviumnetworks.com>
>> CC: Adrien Mazarguil <adrien.mazarguil at 6wind.com>, Nélio Laranjeiro
>> <nelio.laranjeiro at 6wind.com>, "bruce.richardson at intel.com"
>> <bruce.richardson at intel.com>, "Ananyev, Konstantin"
>> <konstantin.ananyev at intel.com>, Chao Zhu <chaozhu at linux.vnet.ibm.com>,
>> "dev at dpdk.org" <dev at dpdk.org>
>> Subject: Re: [dpdk-dev] [PATCH v3 1/8] eal: introduce DMA memory barriers
>> 
>> 
>>> On Jan 18, 2018, at 11:16 PM, Andrew Rybchenko <arybchenko at solarflare.com> wrote:
>>> 
>>> On 01/19/2018 03:44 AM, Yongseok Koh wrote:
>>>> This commit introduces rte_dma_wmb() and rte_dma_rmb(), in order to
>>>> guarantee the ordering of coherent shared memory between the CPU and a DMA
>>>> capable device.
>>>> 
>>>> Signed-off-by: Yongseok Koh 
>>>> <yskoh at mellanox.com>
>>> 
>>> Acked-by: Andrew Rybchenko <arybchenko at solarflare.com>
>>> 
>>> It is already really good. Many thanks.
>> 
>> Thank you!
>> 
>>> Maybe it would be useful to:
>>> - avoid duplication of so long explanations (put in in one place and add reference?)
>> 
>> May have to ask Thomas how to do this. Thomas?
>> 
>>> - explain why it is bound to DMA or call it in a different way, since right now it is bound
>>>   to coherent-mapped IO (rte_cio_rmb() ?). Yes, I see benefits to follow Linux
>>>   terminology, but may be DPDK can do better :) I just add my concerns, but let
>>>   EAL code maintainers to decide
>> 
>> Good idea. Like to hear from other people. But, following linux terms sometime
>> could be good to welcome developers from kernel community to DPDK world. :-)
>> 
>> To people in the cc list, any other concerns?
>> Especially ARM users - Jianbo and Jerin?
> 
> I like Andrew's suggestion. IMO, rte_cio_?mb() makes more sense.

If there's no more suggestion or objection, will send out v3 with the changes requested here by Andrew.

Thank you for reviews and comments.

Yongseok



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