From: Pavel Begunkov <asml.silence@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Jason Gunthorpe" <jgg@ziepe.ca>,
"Mina Almasry" <almasrymina@google.com>,
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Subject: Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers
Date: Wed, 8 May 2024 18:02:14 +0100 [thread overview]
Message-ID: <8ced4c49-d153-40fb-9e62-0a5784cfa864@gmail.com> (raw)
In-Reply-To: <ZjufddNVJs5Csaix@infradead.org>
On 5/8/24 16:51, Christoph Hellwig wrote:
> On Wed, May 08, 2024 at 12:35:52PM +0100, Pavel Begunkov wrote:
>>> all these, because e.g. ttm internally does have a page pool because
>>> depending upon allocator, that's indeed beneficial. Other drm drivers have
>>> more buffer-based concepts for opportunistically memory around, usually
>>> by marking buffers that are just kept as cache as purgeable (which is a
>>> concept that goes all the way to opengl/vulkan).
>>
>> Because in this case it solves nothing and helps with nothing, quite
>> the opposite. Just as well we can ask why NVMe doesn't wrap user pages
>> into a dmabuf while doing IO.
>
> You seem to confused totally unrelated things.
>
> For short-term pins, that is pin_user_pages without FOLL_LONGTERM there
> would never be any point in using a dmabuf as the pin is transient. For
> long-term pin dmabufs in the block layer absolutely make sense, and I
Well, the example fell flat, but you don't use dmabuf when there are
no upsides from using it. For instance, when you already have pinned
pages, you're going to use pages, and there are no other refcounting
concerns. Unless there is an advantage of dmabufs over FOLL_LONGTERM
that I don't know about when used with normal user pages.
> wish io_uring would have just implemented them from the start instead of
> the current fixed buffers that are not quite as useful by not
> pre-mapping DMA and not supporting P2P.
fdget(dmabuf) would be horrible, I assume that's not the suggestion.
But then it's really about kernel internals, and theoretically can
be patched to wrap user pages into a dmabuf and pass it in. The tricky
part is how that "pass it in" should looks like. Keith tried to cover
both pre-mapping and p2p by registering dmabuf and passing the mapped
addresses in an iter IIRC.
Anyway, this discussion should better move from to block/fs lists,
if there is any interest.
--
Pavel Begunkov
next prev parent reply other threads:[~2024-05-08 17:02 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 0:20 [RFC PATCH net-next v8 00/14] Device Memory TCP Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 01/14] queue_api: define queue api Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers Mina Almasry
[not found] ` <ZjH1QaSSQ98mw158@infradead.org>
2024-05-03 20:10 ` Mina Almasry
[not found] ` <ZjjHUh1eINPg1wkn@infradead.org>
2024-05-07 16:05 ` Pavel Begunkov
2024-05-07 16:18 ` Jason Gunthorpe
[not found] ` <ZjpVfPqGNfE5N4bl@infradead.org>
2024-05-07 16:42 ` Mina Almasry
2024-05-07 16:48 ` Jason Gunthorpe
2024-05-07 17:19 ` Daniel Vetter
2024-05-07 17:25 ` Pavel Begunkov
2024-05-07 17:56 ` Jason Gunthorpe
2024-05-07 19:35 ` Pavel Begunkov
2024-05-07 23:32 ` Jason Gunthorpe
2024-05-08 7:16 ` Daniel Vetter
2024-05-08 11:35 ` Pavel Begunkov
2024-05-08 15:34 ` Daniel Vetter
[not found] ` <ZjufddNVJs5Csaix@infradead.org>
2024-05-08 17:02 ` Pavel Begunkov [this message]
2024-05-08 11:30 ` Pavel Begunkov
2024-05-08 14:25 ` Jason Gunthorpe
2024-05-08 15:44 ` Pavel Begunkov
2024-05-08 15:58 ` Jason Gunthorpe
2024-05-08 16:13 ` Pavel Begunkov
2024-05-07 17:17 ` Pavel Begunkov
2024-05-07 16:55 ` Pavel Begunkov
2024-05-07 17:15 ` Mina Almasry
2024-05-07 17:34 ` Pavel Begunkov
2024-04-03 0:20 ` [RFC PATCH net-next v8 03/14] net: netdev netlink api to bind dma-buf to a net device Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 04/14] netdev: support binding dma-buf to netdevice Mina Almasry
2024-04-24 17:35 ` David Wei
2024-04-24 22:11 ` Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 05/14] netdev: netdevice devmem allocator Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 06/14] page_pool: convert to use netmem Mina Almasry
2024-04-03 17:27 ` Simon Horman
2024-04-03 0:20 ` [RFC PATCH net-next v8 07/14] page_pool: devmem support Mina Almasry
2024-04-27 0:17 ` David Wei
2024-04-27 2:11 ` Mina Almasry
2024-04-30 13:31 ` Pavel Begunkov
2024-04-30 13:45 ` Jens Axboe
2024-04-30 18:29 ` Mina Almasry
2024-04-30 18:55 ` Jens Axboe
2024-04-30 19:19 ` Mina Almasry
2024-05-01 13:58 ` Jesper Dangaard Brouer
[not found] ` <ZjH1hO8qJgOqNKub@infradead.org>
2024-05-06 0:29 ` David Wei
2024-04-03 0:20 ` [RFC PATCH net-next v8 08/14] memory-provider: dmabuf devmem memory provider Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 09/14] net: support non paged skb frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 10/14] net: add support for skbs with unreadable frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 11/14] tcp: RX path for devmem TCP Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 12/14] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags Mina Almasry
2024-04-03 0:20 ` [RFC PATCH net-next v8 13/14] net: add devmem TCP documentation Mina Almasry
2024-05-03 13:14 ` Bagas Sanjaya
2024-04-03 0:20 ` [RFC PATCH net-next v8 14/14] selftests: add ncdevmem, netcat for devmem TCP Mina Almasry
2024-04-08 15:57 ` Cong Wang
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