Keep track of no. of non-empty slots on window.

Keep track of no. of non-empty slots on window so that
when number is 0, there are no operations needed to
be processed and we can ignore that window.
Signed-off-by: Pavan Balaji <balaji@anl.gov>

src/mpid/ch3/include/mpid_rma_oplist.h

@@ -167,6 +167,9 @@ static inline int MPIDI_CH3I_Win_create_target(MPID_Win * win_ptr, int target_ra
 
     t->target_rank = target_rank;
 
+    if (slot->target_list == NULL)
+        win_ptr->non_empty_slots++;
+
     /* Enqueue target into target list. */
     MPL_LL_APPEND(slot->target_list, slot->target_list_tail, t);
 
@@ -287,6 +290,9 @@ static inline int MPIDI_CH3I_Win_target_dequeue_and_free(MPID_Win * win_ptr,
     mpi_errno = MPIDI_CH3I_Win_target_free(win_ptr, e);
     if (mpi_errno != MPI_SUCCESS) MPIU_ERR_POP(mpi_errno);
 
+    if (slot->target_list == NULL)
+        win_ptr->non_empty_slots--;
+
  fn_exit:
     return mpi_errno;
  fn_fail:

src/mpid/ch3/include/mpidpre.h

@@ -367,6 +367,7 @@ struct MPIDI_Win_target_state {
         enum MPIDI_RMA_states access_state;                              \
         enum MPIDI_RMA_states exposure_state;                            \
     } states;                                                            \
+    int non_empty_slots;                                                 \
 
 #ifdef MPIDI_CH3_WIN_DECL
 #define MPID_DEV_WIN_DECL \

src/mpid/ch3/src/mpid_rma.c

@@ -331,6 +331,7 @@ static int win_init(MPI_Aint size, int disp_unit, int create_flavor, int model,
     (*win_ptr)->shm_allocated = FALSE;
     (*win_ptr)->states.access_state = MPIDI_RMA_NONE;
     (*win_ptr)->states.exposure_state = MPIDI_RMA_NONE;
+    (*win_ptr)->non_empty_slots = 0;
 
     /* Initialize the passive target lock state */
     MPIU_CHKPMEM_MALLOC((*win_ptr)->targets, struct MPIDI_Win_target_state *,