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From: Kui-Feng Lee <sinquersw@gmail.com>
To: Stephen Hemminger <stephen@networkplumber.org>,
	Kui-Feng Lee <kuifeng@meta.com>
Cc: bpf@vger.kernel.org, ast@kernel.org, martin.lau@linux.dev,
	song@kernel.org, kernel-team@meta.com, andrii@kernel.org,
	sdf@google.com, netdev@vger.kernel.org
Subject: Re: [PATCH bpf-next v6 2/8] net: Update an existing TCP congestion control algorithm.
Date: Mon, 13 Mar 2023 09:43:34 -0700	[thread overview]
Message-ID: <49fa2455-f591-3062-9780-dadadbf388c8@gmail.com> (raw)
In-Reply-To: <ec19df13-0f0a-d05b-f2a2-6e8cfe072fa5@gmail.com>



On 3/13/23 08:46, Kui-Feng Lee wrote:
> 
> 
> On 3/10/23 08:47, Stephen Hemminger wrote:
>> On Thu, 9 Mar 2023 20:38:07 -0800
>> Kui-Feng Lee <kuifeng@meta.com> wrote:
>>
>>> This feature lets you immediately transition to another congestion
>>> control algorithm or implementation with the same name.  Once a name
>>> is updated, new connections will apply this new algorithm.
>>>
>>> Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
>>
>> What is the use case and userspace API for this?
>> The congestion control algorithm normally doesn't allow this because
>> algorithm specific variables (current state of connection) may not
>> work with another algorithm.
> 
> Only new connections will apply the new algorithm, while
> existing connections keep using the algorithm applied. It shouldn't
> have the per-connection state/variable issue you mentioned.
> 
> It will be used to upgrade an existing algorithm to a new version.
> The userspace API is used in the 8th patch of this patchset.
> One of examples in the testcase is
> 
>    link = bpf_map__attach_struct_ops(skel->maps.ca_update_1);
>    .......
>    err = bpf_link__update_map(link, skel->maps.ca_update_2);
> 
> Calling bpf_link__update_map(...) will register ca_pupdate_2 and
> unregister ca_update_1 with the same name
> in one call.  However, the existing connections that has applied
> ca_update_1 keep using the algorithm except someone call
> setsockopt(TCP_CONGESTION, ...) on them.

FYI!
The thread head of the patchset is
  https://lore.kernel.org/all/20230310043812.3087672-1-kuifeng@meta.com/


> 
> 
> 
>>
>> Seems like you are opening Pandora's box here.
> 

  reply	other threads:[~2023-03-13 16:43 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-10  4:38 [PATCH bpf-next v6 0/8] Transit between BPF TCP congestion controls Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 1/8] bpf: Retire the struct_ops map kvalue->refcnt Kui-Feng Lee
2023-03-14  6:05   ` Martin KaFai Lau
2023-03-10  4:38 ` [PATCH bpf-next v6 2/8] net: Update an existing TCP congestion control algorithm Kui-Feng Lee
2023-03-10 16:47   ` Stephen Hemminger
2023-03-13 15:46     ` Kui-Feng Lee
2023-03-13 16:43       ` Kui-Feng Lee [this message]
2023-03-14  0:28   ` Martin KaFai Lau
2023-03-14  4:31     ` Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 3/8] bpf: Create links for BPF struct_ops maps Kui-Feng Lee
2023-03-14  1:42   ` Martin KaFai Lau
2023-03-16  0:21     ` Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 4/8] libbpf: Create a bpf_link in bpf_map__attach_struct_ops() Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 5/8] bpf: Update the struct_ops of a bpf_link Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 6/8] libbpf: Update a bpf_link with another struct_ops Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 7/8] libbpf: Use .struct_ops.link section to indicate a struct_ops with a link Kui-Feng Lee
2023-03-10  4:38 ` [PATCH bpf-next v6 8/8] selftests/bpf: Test switching TCP Congestion Control algorithms Kui-Feng Lee
2023-03-14  5:04   ` Martin KaFai Lau
2023-03-10 16:28 ` [PATCH bpf-next v6 0/8] Transit between BPF TCP congestion controls Kui-Feng Lee

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