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From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Shahaf Shuler <shahafs@mellanox.com>,
	Alejandro Lucero <alejandro.lucero@netronome.com>
Cc: Yongseok Koh <yskoh@mellanox.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	 Ferruh Yigit <ferruh.yigit@intel.com>,
	"nhorman@tuxdriver.com" <nhorman@tuxdriver.com>,
	Gaetan Rivet <gaetan.rivet@6wind.com>, dev <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for external memory
Date: Thu, 14 Feb 2019 16:19:55 +0000	[thread overview]
Message-ID: <ec715d6e-2db5-6645-485f-f0db93e2b058@intel.com> (raw)
In-Reply-To: <AM6PR0502MB37974B11ADAC93B6419D957DC3670@AM6PR0502MB3797.eurprd05.prod.outlook.com>

On 14-Feb-19 1:28 PM, Shahaf Shuler wrote:
> Thursday, February 14, 2019 12:19 PM, Burakov, Anatoly:
>> Subject: Re: [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for
>> external memory
>>
>> On 13-Feb-19 7:24 PM, Shahaf Shuler wrote:
>>> Wednesday, February 13, 2019 1:43 PM, Alejandro Lucero:
>>>> Subject: Re: [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for
>>>> external memory
>>>>
>>>> On Wed, Feb 13, 2019 at 9:11 AM Shahaf Shuler
>> <shahafs@mellanox.com>
>>>> wrote:
>>>>
>>>>> This series is in continue to RFC[1].
>>>>>
>>>>> The DPDK APIs expose 3 different modes to work with memory used for
>>>> DMA:
>>>>>
>>>>> 1. Use the DPDK owned memory (backed by the DPDK provided
>>>> hugepages).
>>>>> This memory is allocated by the DPDK libraries, included in the DPDK
>>>>> memory system (memseg lists) and automatically DMA mapped by the
>>>> DPDK
>>>>> layers.
>>>>>
>>>>> 2. Use memory allocated by the user and register to the DPDK memory
>>>>> systems. This is also referred as external memory. Upon registration
>>>>> of the external memory, the DPDK layers will DMA map it to all
>>>>> needed devices.
>>>>>
>>>>> 3. Use memory allocated by the user and not registered to the DPDK
>>>>> memory system. This is for users who wants to have tight control on
>>>>> this memory. The user will need to explicitly call DMA map function
>>>>> in order to register such memory to the different devices.
>>>>>
>>>>> The scope of the patch focus on #3 above.
>>>>>
>>>>>
>>>> Why can not we have case 2 covering case 3?
>>>
>>> Because it is not our choice rather the DPDK application.
>>> We could not allow it, and force the application to register their external
>> memory to the DPDK memory management system. However IMO it will be
>> wrong.
>>> The use case exists  - some application wants to manage their memory by
>> themselves. w/o the extra overhead of rte_malloc, without creating a special
>> socket to populate the memory and without redundant API calls to
>> rte_extmem_*.
>>>
>>> Simply allocate chunk of memory, DMA map it to device and that’s it.
>>
>> Just a small note: while this sounds good on paper, i should point out that at
>> least *registering* the memory with DPDK is a necessity. You may see
>> rte_extmem_* calls as redundant (and i agree, to an extent), but we don't
>> advertise our PMD's capabilities in a way that makes it easy to determine
>> whether a particular PMD will or will not work without registering external
>> memory within DPDK (i.e. does it use
>> rte_virt2memseg() internally, for example).
>>
>> So, extmem register calls are a necessary evil in such case, and IMO should
>> be called out as required for such external memory usage scenario.
> 
> If we are going to force all to use the extmem, then there is no need w/ this API. we can have the PMDs to register when the memory is registered.
> We can just drop the vfio_dma_map APIs and that's it.
> 

Well, whether we needed it or not is not really my call, but what i can 
say is that using extmem_register is _necessary_ if you're going to use 
the PMD's. You're right, we could just map memory for DMA at register 
time - that would save one API call to get the memory working. It makes 
it a bit weird semantically, but i think we can live with that :)

-- 
Thanks,
Anatoly

  reply	other threads:[~2019-02-14 16:19 UTC|newest]

Thread overview: 79+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-13  9:10 Shahaf Shuler
2019-02-13  9:10 ` [dpdk-dev] [PATCH 1/6] vfio: allow DMA map of memory for the default vfio fd Shahaf Shuler
2019-02-13  9:45   ` Gaëtan Rivet
2019-02-13 11:38     ` Gaëtan Rivet
2019-02-13 15:23     ` Shahaf Shuler
2019-02-13 14:41   ` Burakov, Anatoly
2019-02-13  9:10 ` [dpdk-dev] [PATCH 2/6] vfio: don't fail to DMA map if memory is already mapped Shahaf Shuler
2019-02-13  9:58   ` Gaëtan Rivet
2019-02-13 19:52     ` Shahaf Shuler
2019-02-13  9:10 ` [dpdk-dev] [PATCH 3/6] bus: introduce DMA memory mapping for external memory Shahaf Shuler
2019-02-13 11:17   ` Gaëtan Rivet
2019-02-13 19:07     ` Shahaf Shuler
2019-02-14 14:00       ` Gaëtan Rivet
2019-02-17  6:23         ` Shahaf Shuler
2019-02-13  9:10 ` [dpdk-dev] [PATCH 4/6] net/mlx5: refactor external memory registration Shahaf Shuler
2019-02-13  9:10 ` [dpdk-dev] [PATCH 5/6] net/mlx5: support PCI device DMA map and unmap Shahaf Shuler
2019-02-13 11:35   ` Gaëtan Rivet
2019-02-13 11:44     ` Gaëtan Rivet
2019-02-13 19:11       ` Shahaf Shuler
2019-02-14 10:21         ` Gaëtan Rivet
2019-02-21  9:21           ` Shahaf Shuler
2019-02-13  9:10 ` [dpdk-dev] [PATCH 6/6] doc: deprecate VFIO DMA map APIs Shahaf Shuler
2019-02-13 11:43 ` [dpdk-dev] [PATCH 0/6] introduce DMA memory mapping for external memory Alejandro Lucero
2019-02-13 19:24   ` Shahaf Shuler
2019-02-14 10:19     ` Burakov, Anatoly
2019-02-14 13:28       ` Shahaf Shuler
2019-02-14 16:19         ` Burakov, Anatoly [this message]
2019-02-17  6:18           ` Shahaf Shuler
2019-02-18 12:21             ` Burakov, Anatoly
2019-02-14 12:22     ` Alejandro Lucero
2019-02-14 12:27       ` Alejandro Lucero
2019-02-14 13:41       ` Shahaf Shuler
2019-02-14 16:43         ` Burakov, Anatoly
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 " Shahaf Shuler
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 " Shahaf Shuler
2019-03-10  8:27     ` [dpdk-dev] [PATCH v4 " Shahaf Shuler
2019-03-10  8:27       ` [dpdk-dev] [PATCH v4 1/6] vfio: allow DMA map of memory for the default vfio fd Shahaf Shuler
2019-03-30  0:23         ` Thomas Monjalon
2019-03-30  0:23           ` Thomas Monjalon
2019-03-30 14:29           ` Thomas Monjalon
2019-03-30 14:29             ` Thomas Monjalon
2019-03-10  8:27       ` [dpdk-dev] [PATCH v4 2/6] vfio: don't fail to DMA map if memory is already mapped Shahaf Shuler
2019-03-10  8:28       ` [dpdk-dev] [PATCH v4 3/6] bus: introduce device level DMA memory mapping Shahaf Shuler
2019-03-11 10:19         ` Burakov, Anatoly
2019-03-13  9:56         ` Thomas Monjalon
2019-03-13 11:12           ` Shahaf Shuler
2019-03-13 11:19             ` Thomas Monjalon
2019-03-13 11:47               ` Burakov, Anatoly
2019-03-30 14:36             ` Thomas Monjalon
2019-03-30 14:36               ` Thomas Monjalon
2019-03-10  8:28       ` [dpdk-dev] [PATCH v4 4/6] net/mlx5: refactor external memory registration Shahaf Shuler
2019-03-10  8:28       ` [dpdk-dev] [PATCH v4 5/6] net/mlx5: support PCI device DMA map and unmap Shahaf Shuler
2019-03-10  8:28       ` [dpdk-dev] [PATCH v4 6/6] doc: deprecation notice for VFIO DMA map APIs Shahaf Shuler
2019-03-11 10:20         ` Burakov, Anatoly
2019-03-11 17:35           ` Rami Rosen
2019-10-01 15:20         ` David Marchand
2019-10-02  4:53           ` Shahaf Shuler
2019-10-02  7:51             ` David Marchand
2019-03-11  9:27       ` [dpdk-dev] [PATCH v4 0/6] introduce DMA memory mapping for external memory Gaëtan Rivet
2019-03-30 14:40       ` Thomas Monjalon
2019-03-30 14:40         ` Thomas Monjalon
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 1/6] vfio: allow DMA map of memory for the default vfio fd Shahaf Shuler
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 2/6] vfio: don't fail to DMA map if memory is already mapped Shahaf Shuler
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 3/6] bus: introduce device level DMA memory mapping Shahaf Shuler
2019-03-05 16:35     ` Burakov, Anatoly
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 4/6] net/mlx5: refactor external memory registration Shahaf Shuler
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 5/6] net/mlx5: support PCI device DMA map and unmap Shahaf Shuler
2019-03-05 13:59   ` [dpdk-dev] [PATCH v3 6/6] doc: deprecation notice for VFIO DMA map APIs Shahaf Shuler
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 1/6] vfio: allow DMA map of memory for the default vfio fd Shahaf Shuler
2019-02-28 11:56   ` Burakov, Anatoly
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 2/6] vfio: don't fail to DMA map if memory is already mapped Shahaf Shuler
2019-02-28 11:58   ` Burakov, Anatoly
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 3/6] bus: introduce device level DMA memory mapping Shahaf Shuler
2019-02-28 12:14   ` Burakov, Anatoly
2019-02-28 14:41     ` Burakov, Anatoly
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 4/6] net/mlx5: refactor external memory registration Shahaf Shuler
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 5/6] net/mlx5: support PCI device DMA map and unmap Shahaf Shuler
2019-02-21 14:50 ` [dpdk-dev] [PATCH v2 6/6] doc: deprecate VFIO DMA map APIs Shahaf Shuler
2019-02-21 15:50   ` David Marchand

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