The length of the iov array created by sendMany may exceed UIO_MAXIOV

[edsko]

When sending large payloads (the boundary is somewhere between 33439816 bytes, which is okay, and 33439824 bytes, which is not) the length of the array created by sendMany and then passed to writev goes from 1024 to 1025, at which point writev returns an error which is then thrown as "writev: invalid argument (Invalid argument)" exception.

[dcoutts]

(In case it's not obvious, we hit this when testing Cloud Haskell)

[tibbe]

@edsko It would be great if you can try this patch to make sure it works.

Note, sending a large number of chunks to sendMany is likely to result in subpar performance. On Linux you should send <= 16 chunks for best performance.

[edsko]

Thanks @tibbe. I can confirm that this fixes the problem. Will make a note of your words of caution about the number of chunks.