epoll: eliminate unnecessary lock for zero timeout

We call ep_events_available() under lock when timeout is 0, and then call
it without locks in the loop for the other cases.

Instead, call ep_events_available() without lock for all cases.  For
non-zero timeouts, we will recheck after adding the thread to the wait
queue.  For zero timeout cases, by definition, user is opportunistically
polling and will have to call epoll_wait again in the future.

Note that this lock was kept in c5a282e9635e9 because the whole loop was
historically under lock.

This patch results in a 1% CPU/RPC reduction in RPC benchmarks.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Soheil Hassas Yeganeh <[email protected]>
Suggested-by: Eric Dumazet <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Reviewed-by: Willem de Bruijn <[email protected]>
Reviewed-by: Khazhismel Kumykov <[email protected]>
Cc: Guantao Liu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions