From: Soheil Hassas Yeganeh <[email protected]> ep_events_available() is called multiple times around the busy loop logic, even though the logic is generally not used. ep_reset_busy_poll_napi_id() is similarly always called, even when busy loop is not used.
Eliminate ep_reset_busy_poll_napi_id() and inline it inside ep_busy_loop(). Make ep_busy_loop() return whether there are any events available after the busy loop. This will eliminate unnecessary loads and branches, and simplifies the loop. Signed-off-by: Soheil Hassas Yeganeh <[email protected]> Reviewed-by: Eric Dumazet <[email protected]> Reviewed-by: Willem de Bruijn <[email protected]> Reviewed-by: Khazhismel Kumykov <[email protected]> --- fs/eventpoll.c | 42 +++++++++++++++++++----------------------- 1 file changed, 19 insertions(+), 23 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 5226b0cb1098..28c1d341d2e6 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -391,19 +391,26 @@ static bool ep_busy_loop_end(void *p, unsigned long start_time) * busy loop will return if need_resched or ep_events_available. * * we must do our busy polling with irqs enabled + * + * Returns whether new events are available after a successful busy loop. */ -static void ep_busy_loop(struct eventpoll *ep, int nonblock) +static bool ep_busy_loop(struct eventpoll *ep, int nonblock) { unsigned int napi_id = READ_ONCE(ep->napi_id); - if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) + if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) { napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep); -} - -static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) -{ - if (ep->napi_id) + if (ep_events_available(ep)) + return true; + /* + * Busy poll timed out. Drop NAPI ID for now, we can add + * it back in when we have moved a socket with a valid NAPI + * ID onto the ready list. + */ ep->napi_id = 0; + return false; + } + return false; } /* @@ -444,12 +451,9 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) #else -static inline void ep_busy_loop(struct eventpoll *ep, int nonblock) -{ -} - -static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep) +static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) { + return false; } static inline void ep_set_busy_poll_napi_id(struct epitem *epi) @@ -1857,21 +1861,13 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, } fetch_events: - - if (!ep_events_available(ep)) - ep_busy_loop(ep, timed_out); - eavail = ep_events_available(ep); + if (!eavail) + eavail = ep_busy_loop(ep, timed_out); + if (eavail) goto send_events; - /* - * Busy poll timed out. Drop NAPI ID for now, we can add - * it back in when we have moved a socket with a valid NAPI - * ID onto the ready list. - */ - ep_reset_busy_poll_napi_id(ep); - do { if (signal_pending(current)) return -EINTR; -- 2.29.1.341.ge80a0c044ae-goog
