man/io_uring_prep_recv: expand on how to handle bundles

[romange]

Specifically, explain how to identify multiple buffer ids upon bundle completion.

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git request-pull output:

The following changes since commit a5dd7f85d4b667aeb687afc562ff9750044b42c2:

  man/io_uring_clone_buffers: mention that both rings must share mm (2025-01-14 11:06:56 -0700)

are available in the Git repository at:

  https://github.com/romange/liburing Pr1

for you to fetch changes up to 73bb0ac90437f87b8ecbde50fe30fa25a4df1ae5:

  man/io_uring_prep_recv: expand on how to handle bundles (2025-02-03 14:37:41 +0200)

----------------------------------------------------------------
Roman Gershman (1):
      man/io_uring_prep_recv: expand on how to handle bundles

 man/io_uring_prep_recv.3 | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

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Fixes: https://github.com/axboe/liburing/issues/402
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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[romange]

Consider this a draft. Once the wording is finalized I will copy it to another man page where we duplicate the explanation about bundles. In addition, I can add the necessary code to proxy.c (as part of this PR or separately)

[romange]

Done. Also added the proxy changes. How do you usually test proxy? with what loadtest program?

[axboe]

Please squash the fixup commit to retain some git hygiene, there's no point in having fixup commits in the log.

[axboe]

How do you usually test proxy? with what loadtest program?

Most testing I've done has just been with a simple test program I wrote, which spawns N threads sending M sized buffers. In other words, I think anything really will work, just ensure you have recv bundles enabled of course. If it were me, I'd test one in sink mode, and one in fwd mode where it just dumps it to ncat or something.

[romange]

@axboe I've done some basic testing with proxy but i am not really happy with the level of testing I could do.
When I tried to do something more sophisticated I've stumbled upon #1338 (not related to my changes) which prevents me to test it further. Unfortunately, I do not have time to fix #1338, so I see two options here:

1. I am reverting my proxy changes and submit only the docs PR.
2. You are ok with submitting my proxy changes based on your review.

[axboe]

Let's do the man page separately, it really should be two separate commits to begin with as they aren't directly related. A separate PR for the proxy change would be useful, then I can test it (and fix that other issue) when time arises. It's not really that urgent.