Re: [RFC -next 00/10] Add ZC notifications to splice and sendfile

Pavel Begunkov
2025-03-21T20:50:51Z

On 3/21/25 07:55, Stefan Metzmacher wrote:
> Am 20.03.25 um 11:46 schrieb Pavel Begunkov:
>> On 3/19/25 19:15, Stefan Metzmacher wrote:
>>> Am 19.03.25 um 19:37 schrieb Jens Axboe:
>>>> On 3/19/25 11:45 AM, Joe Damato wrote:
>>>>> On Wed, Mar 19, 2025 at 11:20:50AM -0600, Jens Axboe wrote:
>> ...
>>>> My argument would be the same as for other features - if you can do it
>>>> simpler this other way, why not consider that? The end result would be
>>>> the same, you can do fast sendfile() with sane buffer reuse. But the
>>>> kernel side would be simpler, which is always a kernel main goal for
>>>> those of us that have to maintain it.
>>>>
>>>> Just adding sendfile2() works in the sense that it's an easier drop in
>>>> replacement for an app, though the error queue side does mean it needs
>>>> to change anyway - it's not just replacing one syscall with another. And
>>>> if we want to be lazy, sure that's fine. I just don't think it's the
>>>> best way to do it when we literally have a mechanism that's designed for
>>>> this and works with reuse already with normal send zc (and receive side
>>>> too, in the next kernel).
>>>
>>> A few month (or even years) back, Pavel came up with an idea
>>> to implement some kind of splice into a fixed buffer, if that
>>> would be implemented I guess it would help me in Samba too.
>>> My first usage was on the receive side (from the network).
>>
>> I did it as a testing ground for infra needed for ublk zerocopy,
>> but if that's of interest I can resurrect the patches and see
>> where it goes, especially since the aforementioned infra just got
>> queued.
>
> Would be great!
>
> Have you posted the work in progress somewhere?

Nope apart from a dirty hack I believe I posted back then.

--
Pavel Begunkov