On Sat, Jan 20, 2024 at 12:42:47AM +0000, Joe Damato wrote:

Add F_EPOLL_{S,G}ET_BUSY_POLL_USECS to allow setting a busy poll timeout
per epoll instance so that individual applications can enable (or
disable) epoll based busy poll as needed.

Prior to this change, epoll-based busy poll could only be enabled
system-wide, which limits the usefulness of busy poll.

Signed-off-by: Joe Damato <redacted>
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This should be an ioctl on the epoll fd, not a fcntl(). fcntl()s
should aim to be generic which this isn't. We've recently rejected a
memfd addition as a fcntl() as well for the same reason.