Re: [PATCH 0/8] Add support for vectored registered buffers

[Pavel Begunkov <asml.silence@gmail.com>]

On 3/4/25 00:34, Caleb Sander Mateos wrote:
> On Mon, Mar 3, 2025 at 7:51 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>
>> Add registered buffer support for vectored io_uring operations. That
>> allows to pass an iovec, all entries of which must belong to and
>> point into the same registered buffer specified by sqe->buf_index.
>>
>> The series covers zerocopy sendmsg and reads / writes. Reads and
>> writes are implemented as new opcodes, while zerocopy sendmsg
>> reuses IORING_RECVSEND_FIXED_BUF for the api.
>>
>> Results are aligned to what one would expect from registered buffers:
>>
>> t/io_uring + nullblk, single segment 16K:
>>    34 -> 46 GiB/s
>> examples/send-zerocopy.c default send size (64KB):
>>    82558 -> 123855 MB/s
> 
> Thanks for implementing this, it's great to be able to combine these 2
> optimizations! Though I suspect many applications will want to perform
> vectorized I/O using iovecs that come from different registered
> buffers (e.g. separate header and data allocations). Perhaps a future
> improvement could allow a list of buffer indices to be specified.

That's the design decision made, otherwise the API is becoming a mess
as well as handling. The user has to be smart and keep a small number
of large registered buffers and potentially growing them, which is a
good thing regardless of this feature.

-- 
Pavel Begunkov