On Thu, 4 Jun 2026 at 08:53, Willy Tarreau [off-list ref] wrote:

quoted

It looks like you're actually doing exactly the thing that I thought
was crazy and wouldn't even work reliably: you change the
common_response[] contents dynamically *after* the vmsplice, and
depend on the fact that changing it in user space changes the buffer
in the pipe too.

No no, it's definitely not doing that (or it's a bug, but it's not
supposed to happen). I'm perfectly aware that one must definitely not
do that, and it's a guarantee the user of vmsplice() must provide.

Whew, good.

In that case, can you just try the vmsplice patch series (Christian
already found a bug, but I don't think it will necessarily matter in
practice - famous last words) and that test patch of mine, and see if
it all (a) works for you and (b) if you have any numbers for
performance that would be *great*.

There aren't many obvious splice users out there, and even if they
were to exist they are typically specialized enough that you have to
have a real use case to then tell if the patches make a difference in
real life or not.

So you testing that thing would seem to be a great first test of
whether any of this is realistic..

               Linus