net: rename low latency sockets functions to busy poll

Rename functions in include/net/ll_poll.h to busy wait.
Clarify documentation about expected power use increase.
Rename POLL_LL to POLL_BUSY_LOOP.
Add need_resched() testing to poll/select busy loops.

Note, that in select and poll can_busy_poll is dynamic and is
updated continuously to reflect the existence of supported
sockets with valid queue information.

Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 37 insertions, 23 deletions

diff --git a/fs/select.c b/fs/select.c
index f28a58592725..25cac5faf6d6 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -402,9 +402,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 	poll_table *wait;
 	int retval, i, timed_out = 0;
 	unsigned long slack = 0;
-	unsigned int ll_flag = ll_get_flag();
-	u64 ll_start = ll_start_time(ll_flag);
-	u64 ll_time = ll_run_time();
+	unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
+	u64 busy_start = busy_loop_start_time(busy_flag);
+	u64 busy_end = busy_loop_end_time();
 
 	rcu_read_lock();
 	retval = max_select_fd(n, fds);
@@ -427,7 +427,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 	retval = 0;
 	for (;;) {
 		unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
-		bool can_ll = false;
+		bool can_busy_loop = false;
 
 		inp = fds->in; outp = fds->out; exp = fds->ex;
 		rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
@@ -456,7 +456,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 					mask = DEFAULT_POLLMASK;
 					if (f_op && f_op->poll) {
 						wait_key_set(wait, in, out,
-							     bit, ll_flag);
+							     bit, busy_flag);
 						mask = (*f_op->poll)(f.file, wait);
 					}
 					fdput(f);
@@ -475,11 +475,18 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 						retval++;
 						wait->_qproc = NULL;
 					}
-					if (mask & POLL_LL)
-						can_ll = true;
 					/* got something, stop busy polling */
-					if (retval)
-						ll_flag = 0;
+					if (retval) {
+						can_busy_loop = false;
+						busy_flag = 0;
+
+					/*
+					 * only remember a returned
+					 * POLL_BUSY_LOOP if we asked for it
+					 */
+					} else if (busy_flag & mask)
+						can_busy_loop = true;
+
 				}
 			}
 			if (res_in)
@@ -498,8 +505,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 			break;
 		}
 
-		/* only if on, have sockets with POLL_LL and not out of time */
-		if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
+		/* only if found POLL_BUSY_LOOP sockets && not out of time */
+		if (!need_resched() && can_busy_loop &&
+		    busy_loop_range(busy_start, busy_end))
 			continue;
 
 		/*
@@ -734,7 +742,8 @@ struct poll_list {
  * if pwait->_qproc is non-NULL.
  */
 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
-				     bool *can_ll, unsigned int ll_flag)
+				     bool *can_busy_poll,
+				     unsigned int busy_flag)
 {
 	unsigned int mask;
 	int fd;
@@ -748,10 +757,10 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 			mask = DEFAULT_POLLMASK;
 			if (f.file->f_op && f.file->f_op->poll) {
 				pwait->_key = pollfd->events|POLLERR|POLLHUP;
-				pwait->_key |= ll_flag;
+				pwait->_key |= busy_flag;
 				mask = f.file->f_op->poll(f.file, pwait);
-				if (mask & POLL_LL)
-					*can_ll = true;
+				if (mask & busy_flag)
+					*can_busy_poll = true;
 			}
 			/* Mask out unneeded events. */
 			mask &= pollfd->events | POLLERR | POLLHUP;
@@ -770,9 +779,10 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 	ktime_t expire, *to = NULL;
 	int timed_out = 0, count = 0;
 	unsigned long slack = 0;
-	unsigned int ll_flag = ll_get_flag();
-	u64 ll_start = ll_start_time(ll_flag);
-	u64 ll_time = ll_run_time();
+	unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
+	u64 busy_start = busy_loop_start_time(busy_flag);
+	u64 busy_end = busy_loop_end_time();
+
 
 	/* Optimise the no-wait case */
 	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
@@ -785,7 +795,7 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 
 	for (;;) {
 		struct poll_list *walk;
-		bool can_ll = false;
+		bool can_busy_loop = false;
 
 		for (walk = list; walk != NULL; walk = walk->next) {
 			struct pollfd * pfd, * pfd_end;
@@ -800,10 +810,13 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 				 * this. They'll get immediately deregistered
 				 * when we break out and return.
 				 */
-				if (do_pollfd(pfd, pt, &can_ll, ll_flag)) {
+				if (do_pollfd(pfd, pt, &can_busy_loop,
+					      busy_flag)) {
 					count++;
 					pt->_qproc = NULL;
-					ll_flag = 0;
+					/* found something, stop busy polling */
+					busy_flag = 0;
+					can_busy_loop = false;
 				}
 			}
 		}
@@ -820,8 +833,9 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
 		if (count || timed_out)
 			break;
 
-		/* only if on, have sockets with POLL_LL and not out of time */
-		if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
+		/* only if found POLL_BUSY_LOOP sockets && not out of time */
+		if (!need_resched() && can_busy_loop &&
+		    busy_loop_range(busy_start, busy_end))
 			continue;
 
 		/*