From: Paolo Abeni
> Sent: 02 February 2021 10:19
...
> Note that you can already process several packets with a single syscall
> using sendmmsg/recvmmsg. Both have issues with error reporting and
> timeout and IIRC still don't amortize the overhead introduced e.g. by
> CONFIG_HARDENED_USERCOPY.
Both CONFIG_HARDENED_USERCOPY and the extra user copies needed
even for sendmsg() over send() are definitely measurable.
I've run tests using _copy_from_user() for many of the copies.
Even the cost of reading in a single iov[] for the buffer
affects things.
My last attempt at speeding up writev("/dev/null", iov, 10)
fell into the rabbit hole of io_uring (again).
But the partial changes gave a few % improvement.
David
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