From: David Ahern <dsahern@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>, Mina Almasry <almasrymina@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Christoph Hellwig <hch@lst.de>,
John Hubbard <jhubbard@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Jesper Dangaard Brouer <jbrouer@redhat.com>,
brouer@redhat.com, Alexander Duyck <alexander.duyck@gmail.com>,
Yunsheng Lin <linyunsheng@huawei.com>,
davem@davemloft.net, pabeni@redhat.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
Lorenzo Bianconi <lorenzo@kernel.org>,
Yisen Zhuang <yisen.zhuang@huawei.com>,
Salil Mehta <salil.mehta@huawei.com>,
Eric Dumazet <edumazet@google.com>,
Sunil Goutham <sgoutham@marvell.com>,
Geetha sowjanya <gakula@marvell.com>,
Subbaraya Sundeep <sbhatta@marvell.com>,
hariprasad <hkelam@marvell.com>,
Saeed Mahameed <saeedm@nvidia.com>,
Leon Romanovsky <leon@kernel.org>, Felix Fietkau <nbd@nbd.name>,
Ryder Lee <ryder.lee@mediatek.com>,
Shayne Chen <shayne.chen@mediatek.com>,
Sean Wang <sean.wang@mediatek.com>, Kalle Valo <kvalo@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
linux-rdma@vger.kernel.org, linux-wireless@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
Jonathan Lemon <jonathan.lemon@gmail.com>
Subject: Re: Memory providers multiplexing (Was: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE_FRAG flag)
Date: Tue, 11 Jul 2023 15:39:45 -0600 [thread overview]
Message-ID: <2263ae79-690e-8a4d-fca2-31aacc5c9bc6@kernel.org> (raw)
In-Reply-To: <20230711133915.03482fdc@kernel.org>
On 7/11/23 2:39 PM, Jakub Kicinski wrote:
> On Tue, 11 Jul 2023 10:06:28 -0700 Mina Almasry wrote:
>>>> Any reason not to allow an alternative representation for skb frags than
>>>> struct page?
>>>
>>> I don't think there's a hard technical reason. We can make it work.
>>
>> I also think we can switch the representation for skb frags to
>> something else. However - please do correct me if I'm wrong - I don't
>> think that is sufficient for device memory TCP. My understanding is
>> that we also need to modify any NIC drivers that want to use device
>> memory TCP to understand a new memory type, and the page pool as well
>> if that's involved. I think in particular modifying the memory type in
>> all the NIC drivers that want to do device memory TCP is difficult. Do
>> you think this is feasible?
>
> That's why I was thinking about adding an abstraction between
> the page pool and the driver. Instead of feeding driver pages
> a new abstraction could feed the driver just an identifier and a PA.
skb frag is currently a bio_vec. Overloading the 'struct page' address
in that struct with another address is easy to do. Requiring a certain
alignment on the address gives you a few low bits to use a flags / magic
/ etc.
Overloading len and offset is not really possible - way too much code is
affected (e.g., iov walking and MSS / TSO segmenting).
ie., you could overload page address with a pointer to an object in your
new abstraction layer and the struct has the other meta data.
typedef struct skb_frag {
union {
struct bio_vec bvec;
struct new_abstraction abs;
};
} skb_frag_t;
where
struct new_abstraction {
void *addr,
unsigned int len;
unsigned int offset;
};
I have been playing with a similar and it co-exists with the existing
code quite well with the constraint on location of len and offset.
>
> Whether we want to support fragmentation in that model or not would
> have to be decided.
>
> We can take pages from the page pool and feed them to drivers via
> such an API, but drivers need to stop expecting pages.
yes, drivers would have to be updated to understand the new format. A
downside, but again relatively easy to manage.
>
> That's for data buffers only, obviously. We can keep using pages
> and raw page pool for headers.
yes.
next prev parent reply other threads:[~2023-07-11 21:39 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-12 13:02 [PATCH net-next v4 0/5] introduce page_pool_alloc() API Yunsheng Lin
2023-06-12 13:02 ` [PATCH net-next v4 1/5] page_pool: frag API support for 32-bit arch with 64-bit DMA Yunsheng Lin
2023-06-13 13:30 ` Alexander Lobakin
2023-06-14 3:36 ` Yunsheng Lin
2023-06-14 3:55 ` Jakub Kicinski
2023-06-14 10:52 ` Alexander Lobakin
2023-06-14 12:15 ` Yunsheng Lin
2023-06-14 12:42 ` Alexander Lobakin
2023-06-14 4:09 ` Jakub Kicinski
2023-06-14 11:42 ` Yunsheng Lin
2023-06-14 17:07 ` Jakub Kicinski
2023-06-15 7:29 ` Yunsheng Lin
2023-06-12 13:02 ` [PATCH net-next v4 2/5] page_pool: unify frag_count handling in page_pool_is_last_frag() Yunsheng Lin
2023-06-14 4:33 ` Jakub Kicinski
2023-06-14 11:55 ` Yunsheng Lin
2023-06-12 13:02 ` [PATCH net-next v4 3/5] page_pool: introduce page_pool_alloc() API Yunsheng Lin
2023-06-13 13:08 ` Alexander Lobakin
2023-06-13 13:11 ` Alexander Lobakin
2023-06-14 3:17 ` Yunsheng Lin
2023-06-12 13:02 ` [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE_FRAG flag Yunsheng Lin
2023-06-14 17:19 ` Jakub Kicinski
2023-06-15 7:17 ` Yunsheng Lin
2023-06-15 16:51 ` Jakub Kicinski
2023-06-15 18:26 ` Alexander Duyck
2023-06-16 12:20 ` Yunsheng Lin
2023-06-16 15:01 ` Alexander Duyck
2023-06-16 18:59 ` Jesper Dangaard Brouer
2023-06-16 19:21 ` Jakub Kicinski
2023-06-16 20:42 ` Memory providers multiplexing (Was: [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE_FRAG flag) Jesper Dangaard Brouer
2023-06-19 18:07 ` Jakub Kicinski
2023-06-20 15:12 ` Jesper Dangaard Brouer
2023-06-20 15:39 ` Jakub Kicinski
2023-06-30 2:27 ` Mina Almasry
2023-07-03 4:20 ` David Ahern
2023-07-03 6:22 ` Mina Almasry
2023-07-03 14:45 ` David Ahern
2023-07-03 17:13 ` Eric Dumazet
2023-07-03 17:23 ` David Ahern
2023-07-06 1:19 ` Mina Almasry
2023-07-03 17:15 ` Eric Dumazet
2023-07-03 17:25 ` David Ahern
2023-07-03 21:43 ` Jason Gunthorpe
2023-07-06 1:17 ` Mina Almasry
2023-07-10 17:44 ` Jason Gunthorpe
2023-07-10 23:02 ` Mina Almasry
2023-07-10 23:49 ` Jason Gunthorpe
2023-07-11 0:45 ` Mina Almasry
2023-07-11 13:11 ` Jason Gunthorpe
2023-07-11 17:24 ` Mina Almasry
2023-07-11 4:27 ` Christoph Hellwig
2023-07-11 4:59 ` Jakub Kicinski
2023-07-11 5:04 ` Christoph Hellwig
2023-07-11 12:05 ` Jason Gunthorpe
2023-07-11 16:00 ` Jakub Kicinski
2023-07-11 16:20 ` David Ahern
2023-07-11 16:32 ` Jakub Kicinski
2023-07-11 17:06 ` Mina Almasry
2023-07-11 20:39 ` Jakub Kicinski
2023-07-11 21:39 ` David Ahern [this message]
2023-07-12 3:42 ` Mina Almasry
2023-07-12 7:55 ` Christian König
2023-07-12 13:03 ` Jason Gunthorpe
2023-07-12 13:35 ` Christian König
2023-07-12 22:41 ` Mina Almasry
2023-07-12 13:01 ` Jason Gunthorpe
2023-07-12 20:16 ` Mina Almasry
2023-07-12 23:57 ` Jason Gunthorpe
2023-07-13 7:56 ` Christian König
2023-07-14 14:55 ` Mina Almasry
2023-07-14 15:18 ` David Ahern
2023-07-17 2:05 ` Mina Almasry
2023-07-17 3:08 ` David Ahern
2023-07-14 15:55 ` Jason Gunthorpe
2023-07-17 1:53 ` Mina Almasry
2023-07-24 14:56 ` Jesper Dangaard Brouer
2023-07-24 16:28 ` Jason Gunthorpe
2023-07-25 4:04 ` Mina Almasry
2023-07-26 17:36 ` Jesper Dangaard Brouer
2023-07-11 16:42 ` Jason Gunthorpe
2023-07-11 17:06 ` Jakub Kicinski
2023-07-11 18:52 ` Jason Gunthorpe
2023-07-11 20:34 ` Jakub Kicinski
2023-07-11 23:56 ` Jason Gunthorpe
2023-07-11 6:52 ` Dan Williams
2023-07-06 16:50 ` Jakub Kicinski
2023-06-17 12:19 ` [PATCH net-next v4 4/5] page_pool: remove PP_FLAG_PAGE_FRAG flag Yunsheng Lin
2023-06-15 13:59 ` Alexander Lobakin
2023-06-12 13:02 ` [PATCH net-next v4 5/5] page_pool: update document about frag API Yunsheng Lin
2023-06-14 4:40 ` Jakub Kicinski
2023-06-14 12:04 ` Yunsheng Lin
2023-06-14 16:56 ` Jakub Kicinski
2023-06-15 6:49 ` Yunsheng Lin
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