From: Pavel Begunkov <asml.silence@gmail.com>
To: Mina Almasry <almasrymina@google.com>
Cc: "Christoph Hellwig" <hch@infradead.org>,
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Subject: Re: [PATCH net-next v10 02/14] net: page_pool: create hooks for custom page providers
Date: Fri, 7 Jun 2024 14:42:53 +0100 [thread overview]
Message-ID: <eb237e6e-3626-4435-8af5-11ed3931b0ac@gmail.com> (raw)
In-Reply-To: <CAHS8izNmT_NzgCu1pY1RKgJh+kP2rCL_90Gqau2Pkd3-48Q1_w@mail.gmail.com>
On 6/3/24 16:43, Mina Almasry wrote:
> On Mon, Jun 3, 2024 at 7:52 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>
>> On 6/3/24 15:17, Mina Almasry wrote:
>>> On Fri, May 31, 2024 at 10:35 PM Christoph Hellwig <hch@infradead.org> wrote:
>>>>
>>>> On Thu, May 30, 2024 at 08:16:01PM +0000, Mina Almasry wrote:
>>>>> I'm unsure if the discussion has been resolved yet. Sending the series
>>>>> anyway to get reviews/feedback on the (unrelated) rest of the series.
>>>>
>>>> As far as I'm concerned it is not. I've not seen any convincing
>>>> argument for more than page/folio allocator including larger order /
>>>> huge page and dmabuf.
>>>>
>>>
>>> Thanks Christoph, this particular patch series adds dmabuf, so I
>>> assume no objection there. I assume the objection is that you want the
>>> generic, extensible hooks removed.
>>>
>>> To be honest, I don't think the hooks are an integral part of the
>>> design, and at this point I think we've argued for them enough. I
>>> think we can easily achieve the same thing with just raw if statements
>>> in a couple of places. We can always add the hooks if and only if we
>>> actually justify many memory providers.
>>>
>>> Any objections to me removing the hooks and directing to memory
>>> allocations via simple if statements? Something like (very rough
>>> draft, doesn't compile):
>>
>> The question for Christoph is what exactly is the objection here? Why we
>> would not be using well defined ops when we know there will be more
>> users? Repeating what I said in the last thread, for io_uring it's used
>> to implement the flow of buffers from userspace to the kernel, the ABI,
>> which is orthogonal to the issue of what memory type it is and how it
>> came there. And even if you mandate unnecessary dmabuf condoms for user
>> memory in one form or another IMHO for no clear reason, the callbacks
>> (or yet another if-else) would still be needed.
>>
>> Sure, Mina can drop and hard code devmem path to easy the pain for
>> him and delay the discussion, but then shortly after I will be
>> re-sending same shit.
>
> You don't need to re-send the same ops again, right? You can add io
> uring support without ops. Something like:
>
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 92be1aaf18ccc..2cc986455bce6 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -557,8 +557,8 @@ netmem_ref page_pool_alloc_netmem(struct page_pool
> *pool, gfp_t gfp)
> return netmem;
>
> /* Slow-path: cache empty, do real allocation */
> - if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_ops)
> - netmem = pool->mp_ops->alloc_pages(pool, gfp);
> + if (unlikely(page_pool_is_dmabuf(pool)))
> + netmem = mp_dmabuf_devmem_alloc_pages():
> + else if (unlikely(page_pool_is_iouring(pool)))
> + netmem = mp_io_uring_alloc_pages():
> else
> netmem = __page_pool_alloc_pages_slow(pool, gfp);
> return netmem;
>
> So IMO, the ops themselves, which Christoph is repeatedly nacking, are
> not that important.
>
> I humbly think the energy should be spent convincing maintainers of
> the use case of io uring memory, not the ops. The ops are a cosmetic
I haven't seen any arguments against from the (net) maintainers so
far. Nor I see any objection against callbacks from them (considering
that either option adds an if).
And just not to confuse folks, it's just user pages, not some
weird special io_uring memory.
> change to the code, and can be added later. Christoph is nacking the
> ops because it gives people too much rope [1].
Yes, it is cosmetic, just as much as removing it is a cosmetic
change. You can apply same "too much rope" argument basically
to anything.
Take io_uring, nothing would change in the process, it'd still
be sent to net and reviewed exactly same way, while being less
clean, with poorer subsystem separation, allowing custom
formats / argument list, etc. I think it's cleaner with callbacks,
Mr. Christoph has other beliefs and keeps coercing to them,
even though from time to time it backfires for the author, just
personal experience.
> But if you disagree and think the ops themselves are important for a
> reason I missed, I'm happy waiting until agreement is reached here.
> Sorry, just voicing my 2 cents.
>
> [1] https://lore.kernel.org/netdev/ZjjHUh1eINPg1wkn@infradead.org/
>
--
Pavel Begunkov
next prev parent reply other threads:[~2024-06-07 13:42 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-30 20:15 [PATCH net-next v10 00/14] Device Memory TCP Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 01/14] netdev: add netdev_rx_queue_restart() Mina Almasry
2024-05-30 23:51 ` David Wei
2024-06-03 12:52 ` Pavel Begunkov
2024-05-30 20:16 ` [PATCH net-next v10 02/14] net: page_pool: create hooks for custom page providers Mina Almasry
2024-06-01 5:35 ` Christoph Hellwig
2024-06-03 14:17 ` Mina Almasry
2024-06-03 14:52 ` Pavel Begunkov
2024-06-03 15:43 ` Mina Almasry
2024-06-07 13:42 ` Pavel Begunkov [this message]
2024-06-07 14:27 ` David Ahern
2024-06-07 14:52 ` Jason Gunthorpe
2024-06-10 0:37 ` David Wei
2024-06-10 1:07 ` Pavel Begunkov
2024-06-10 12:16 ` Jason Gunthorpe
2024-06-10 12:38 ` Christian König
2024-06-10 15:41 ` Mina Almasry
2024-06-10 19:32 ` Pavel Begunkov
2024-06-10 16:22 ` Daniel Vetter
2024-06-11 6:25 ` Christoph Hellwig
2024-06-11 8:21 ` Christian König
2024-06-10 15:16 ` David Ahern
2024-06-10 19:20 ` Pavel Begunkov
2024-06-10 22:15 ` Jason Gunthorpe
2024-06-11 18:09 ` Mina Almasry
2024-06-12 12:06 ` Jason Gunthorpe
2024-06-12 15:47 ` David Ahern
2024-06-17 19:15 ` Pavel Begunkov
2024-06-11 6:26 ` Christoph Hellwig
2024-06-11 17:48 ` Mina Almasry
2024-06-07 15:42 ` Pavel Begunkov
2024-06-07 15:46 ` Pavel Begunkov
2024-06-07 16:59 ` Mina Almasry
2024-06-10 1:12 ` Pavel Begunkov
2024-06-10 0:27 ` David Wei
2024-06-05 8:24 ` Christoph Hellwig
2024-06-07 13:45 ` Pavel Begunkov
2024-06-11 6:34 ` Christoph Hellwig
2024-06-17 18:04 ` Pavel Begunkov
2024-06-18 6:43 ` Christoph Hellwig
2024-06-18 11:40 ` Pavel Begunkov
2024-06-05 8:23 ` Christoph Hellwig
2024-05-30 20:16 ` [PATCH net-next v10 03/14] net: netdev netlink api to bind dma-buf to a net device Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 04/14] netdev: support binding dma-buf to netdevice Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 05/14] netdev: netdevice devmem allocator Mina Almasry
2024-06-04 10:13 ` Paolo Abeni
2024-06-04 16:15 ` Steven Rostedt
2024-06-04 16:31 ` Jason Gunthorpe
2024-06-04 16:42 ` Steven Rostedt
2024-06-04 23:44 ` Andrew Lunn
2024-06-05 0:27 ` Steven Rostedt
2024-06-05 0:52 ` Andrew Lunn
2024-06-06 1:43 ` Steven Rostedt
2024-06-07 7:55 ` Niklas Schnelle
2024-05-30 20:16 ` [PATCH net-next v10 06/14] page_pool: convert to use netmem Mina Almasry
2024-06-04 10:23 ` Paolo Abeni
2024-06-06 1:48 ` Steven Rostedt
2024-06-07 12:31 ` Pavel Begunkov
2024-05-30 20:16 ` [PATCH net-next v10 07/14] page_pool: devmem support Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 08/14] memory-provider: dmabuf devmem memory provider Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 09/14] net: support non paged skb frags Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 10/14] net: add support for skbs with unreadable frags Mina Almasry
2024-06-04 10:46 ` Paolo Abeni
2024-06-06 16:49 ` Mina Almasry
2024-06-06 16:58 ` Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 11/14] tcp: RX path for devmem TCP Mina Almasry
2024-06-04 10:53 ` Paolo Abeni
2024-05-30 20:16 ` [PATCH net-next v10 12/14] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags Mina Almasry
2024-05-30 20:16 ` [PATCH net-next v10 13/14] net: add devmem TCP documentation Mina Almasry
2024-06-01 13:09 ` Bagas Sanjaya
2024-05-30 20:16 ` [PATCH net-next v10 14/14] selftests: add ncdevmem, netcat for devmem TCP Mina Almasry
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