This patch triggers non-blocking busy poll when busy_poll is enabled,
epoll is called with a timeout of 0 and is associated with a napi_id.
This enables an app thread to go through napi poll routine once by
calling epoll with a 0 timeout.
poll/select with a 0 timeout behave in a similar manner.
Signed-off-by: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
v4:
- Fix a typo (Andy)
v3:
- reset napi_id if no event available after busy poll (Alex)
v2:
- Added net_busy_loop_on() check (Eric)
---
fs/eventpoll.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 12eebcdea9c8..10da7a8e1c2b 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1847,6 +1847,22 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
eavail = ep_events_available(ep);
write_unlock_irq(&ep->lock);
+ /*
+ * Trigger non-blocking busy poll if timeout is 0 and there are
+ * no events available. Passing timed_out(1) to ep_busy_loop
+ * will make sure that busy polling is triggered only once.
+ */
+ if (!eavail && net_busy_loop_on()) {
+ ep_busy_loop(ep, timed_out);
+
+ write_lock_irq(&ep->lock);
+ eavail = ep_events_available(ep);
+ write_unlock_irq(&ep->lock);
+
+ if (!eavail)
+ ep_reset_busy_poll_napi_id(ep);
+ }
+
goto send_events;
}
--
2.25.4
