Commit 8a6de262 authored by Martin Karsten's avatar Martin Karsten Committed by Jakub Kicinski
Browse files

eventpoll: Control irq suspension for prefer_busy_poll 



When events are reported to userland and prefer_busy_poll is set, irqs
are temporarily suspended using napi_suspend_irqs.

If no events are found and ep_poll would go to sleep, irq suspension is
cancelled using napi_resume_irqs.

Signed-off-by: default avatarMartin Karsten <mkarsten@uwaterloo.ca>
Co-developed-by: default avatarJoe Damato <jdamato@fastly.com>
Signed-off-by: default avatarJoe Damato <jdamato@fastly.com>
Tested-by: default avatarJoe Damato <jdamato@fastly.com>
Tested-by: default avatarMartin Karsten <mkarsten@uwaterloo.ca>
Acked-by: default avatarStanislav Fomichev <sdf@fomichev.me>
Reviewed-by: default avatarSridhar Samudrala <sridhar.samudrala@intel.com>
Link: https://patch.msgid.link/20241109050245.191288-5-jdamato@fastly.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent ab5b28b0

fs/eventpoll.c

+31 −1
Original line number Diff line number Diff line
@@ -457,6 +457,8 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock) 
		 * it back in when we have moved a socket with a valid NAPI

		 * ID onto the ready list.

		 */

		if (prefer_busy_poll)

			napi_resume_irqs(napi_id);

		ep->napi_id = 0;

		return false;

	}
@@ -540,6 +542,22 @@ static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, 
	}

}



static void ep_suspend_napi_irqs(struct eventpoll *ep)

{

	unsigned int napi_id = READ_ONCE(ep->napi_id);



	if (napi_id >= MIN_NAPI_ID && READ_ONCE(ep->prefer_busy_poll))

		napi_suspend_irqs(napi_id);

}



static void ep_resume_napi_irqs(struct eventpoll *ep)

{

	unsigned int napi_id = READ_ONCE(ep->napi_id);



	if (napi_id >= MIN_NAPI_ID && READ_ONCE(ep->prefer_busy_poll))

		napi_resume_irqs(napi_id);

}



#else



static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
@@ -557,6 +575,14 @@ static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, 
	return -EOPNOTSUPP;

}



static void ep_suspend_napi_irqs(struct eventpoll *ep)

{

}



static void ep_resume_napi_irqs(struct eventpoll *ep)

{

}



#endif /* CONFIG_NET_RX_BUSY_POLL */



/*
@@ -788,6 +814,7 @@ static bool ep_refcount_dec_and_test(struct eventpoll *ep) 


static void ep_free(struct eventpoll *ep)

{

	ep_resume_napi_irqs(ep);

	mutex_destroy(&ep->mtx);

	free_uid(ep->user);

	wakeup_source_unregister(ep->ws);
@@ -2005,9 +2032,12 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, 
			 * trying again in search of more luck.

			 */

			res = ep_send_events(ep, events, maxevents);

			if (res)

			if (res) {

				if (res > 0)

					ep_suspend_napi_irqs(ep);

				return res;

			}

		}



		if (timed_out)

			return 0;