[PATCHSET 0/2] Reduce poll based overhead

[Jens Axboe <axboe@kernel.dk>]

Hi,

Networked workloads are intensive on the poll arming side, as most
receive operations will be triggered async by poll. For that kind
of poll triggering, we have allocated req->apoll dynamically and
that serves as our poll entry. This means that the poll->events
and poll->head are not part of the io_kiocb cachelines, and hence
often not hot in the completion path. When profiling workloads,
io_poll_check_events() shows up as hotter than it should be, exactly
because we have to pull in this cacheline separately.

Cache state in the io_kiocb itself instead, which avoids pulling
in unnecessary data in the poll task_work path. This reduces overhead
by about 3-4%.

-- 
Jens Axboe