Commit 85455c79 authored by Joe Damato's avatar Joe Damato Committed by David S. Miller
Browse files

eventpoll: support busy poll per epoll instance 



Allow busy polling on a per-epoll context basis. The per-epoll context
usec timeout value is preferred, but the pre-existing system wide sysctl
value is still supported if it specified.

busy_poll_usecs is a u32, but in a follow up patch the ioctl provided to
the user only allows setting a value from 0 to S32_MAX.

Signed-off-by: default avatarJoe Damato <jdamato@fastly.com>
Acked-by: default avatarStanislav Fomichev <sdf@google.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 723615a1

fs/eventpoll.c

+39 −5
Original line number Diff line number Diff line
@@ -227,6 +227,8 @@ struct eventpoll { 
#ifdef CONFIG_NET_RX_BUSY_POLL

	/* used to track busy poll napi_id */

	unsigned int napi_id;

	/* busy poll timeout */

	u32 busy_poll_usecs;

#endif



#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -387,11 +389,41 @@ static inline int ep_events_available(struct eventpoll *ep) 
}



#ifdef CONFIG_NET_RX_BUSY_POLL

/**

 * busy_loop_ep_timeout - check if busy poll has timed out. The timeout value

 * from the epoll instance ep is preferred, but if it is not set fallback to

 * the system-wide global via busy_loop_timeout.

 *

 * @start_time: The start time used to compute the remaining time until timeout.

 * @ep: Pointer to the eventpoll context.

 *

 * Return: true if the timeout has expired, false otherwise.

 */

static bool busy_loop_ep_timeout(unsigned long start_time,

				 struct eventpoll *ep)

{

	unsigned long bp_usec = READ_ONCE(ep->busy_poll_usecs);



	if (bp_usec) {

		unsigned long end_time = start_time + bp_usec;

		unsigned long now = busy_loop_current_time();



		return time_after(now, end_time);

	} else {

		return busy_loop_timeout(start_time);

	}

}



static bool ep_busy_loop_on(struct eventpoll *ep)

{

	return !!ep->busy_poll_usecs || net_busy_loop_on();

}



static bool ep_busy_loop_end(void *p, unsigned long start_time)

{

	struct eventpoll *ep = p;



	return ep_events_available(ep) || busy_loop_timeout(start_time);

	return ep_events_available(ep) || busy_loop_ep_timeout(start_time, ep);

}



/*
@@ -404,7 +436,7 @@ 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 && ep_busy_loop_on(ep)) {

		napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false,

			       BUSY_POLL_BUDGET);

		if (ep_events_available(ep))
@@ -425,12 +457,12 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock) 
 */

static inline void ep_set_busy_poll_napi_id(struct epitem *epi)

{

	struct eventpoll *ep;

	struct eventpoll *ep = epi->ep;

	unsigned int napi_id;

	struct socket *sock;

	struct sock *sk;



	if (!net_busy_loop_on())

	if (!ep_busy_loop_on(ep))

		return;



	sock = sock_from_file(epi->ffd.file);
@@ -442,7 +474,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) 
		return;



	napi_id = READ_ONCE(sk->sk_napi_id);

	ep = epi->ep;



	/* Non-NAPI IDs can be rejected

	 *	or
@@ -2058,6 +2089,9 @@ static int do_epoll_create(int flags) 
		error = PTR_ERR(file);

		goto out_free_fd;

	}

#ifdef CONFIG_NET_RX_BUSY_POLL

	ep->busy_poll_usecs = 0;

#endif

	ep->file = file;

	fd_install(fd, file);

	return fd;