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;
 
                 /*