svm: merge want deq and leq threshold notifications

Type: improvement

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I2775af35386a4e52ba82991c68bce6c56f13410f

2 files changed, 8 insertions, 20 deletions

diff --git a/src/plugins/http_static/static_server.c b/src/plugins/http_static/static_server.c
index ba81882fca0..f2c1cfc2d66 100644
--- a/src/plugins/http_static/static_server.c
+++ b/src/plugins/http_static/static_server.c
@@ -31,6 +31,8 @@
  */
 /*? %%clicmd:group_label Static HTTP Server %% ?*/
 
+#define HTTP_FIFO_THRESH (16 << 10)
+
 http_static_server_main_t http_static_server_main;
 
 /** \brief Format the called-from enum
@@ -892,8 +894,7 @@ state_send_more_data (session_t * s, http_session_t * hs,
   if (hs->data_offset < vec_len (hs->data))
     {
       /* No: ask for a shoulder-tap when the tx fifo has space */
-      svm_fifo_add_want_deq_ntf (hs->tx_fifo,
-				 SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH);
+      svm_fifo_add_want_deq_ntf (hs->tx_fifo, SVM_FIFO_WANT_DEQ_NOTIF);
       hs->session_state = HTTP_STATE_SEND_MORE_DATA;
       return 0;
     }
@@ -1057,14 +1058,10 @@ http_static_server_session_accept_callback (session_t * s)
    * full, however avoid entering a state where the
    * fifo is full all the time and small chunks of data are being enqueued
    * each time. If the fifo is small (under 16K) we set
-   * the threshold to 0, meaning a notification will be given when the
+   * the threshold to it's size, meaning a notification will be given when the
    * fifo empties.
    */
-#define HTTP_FIFO_THRESH (16 << 10)
-  thresh = (svm_fifo_size (hs->tx_fifo) < HTTP_FIFO_THRESH) ?
-	     0 :
-	     svm_fifo_size (hs->tx_fifo) - HTTP_FIFO_THRESH;
-
+  thresh = clib_min (svm_fifo_size (hs->tx_fifo), HTTP_FIFO_THRESH);
   svm_fifo_set_deq_thresh (hs->tx_fifo, thresh);
 
   s->session_state = SESSION_STATE_READY;
diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index 42efb5af6b3..9b55f720e5b 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -35,8 +35,6 @@ typedef enum svm_fifo_deq_ntf_
   SVM_FIFO_WANT_DEQ_NOTIF = 1,		/**< Notify on dequeue */
   SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL = 2,	/**< Notify on transition from full */
   SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY = 4, /**< Notify on transition to empty */
-  SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH = 5, /**< Notify on transition to less
-					       than or equal threshold */
 } svm_fifo_deq_ntf_t;
 
 typedef enum svm_fifo_flag_
@@ -795,8 +793,7 @@ svm_fifo_clear_deq_ntf (svm_fifo_t * f)
   /* Set the flag if want_notif_if_full was the only ntf requested */
   f->shr->has_deq_ntf =
     f->shr->want_deq_ntf == SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL;
-  svm_fifo_del_want_deq_ntf (f, SVM_FIFO_WANT_DEQ_NOTIF |
-				  SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH);
+  svm_fifo_del_want_deq_ntf (f, SVM_FIFO_WANT_DEQ_NOTIF);
 }
 
 /**
@@ -832,7 +829,7 @@ svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
   if (PREDICT_TRUE (want_ntf == SVM_FIFO_NO_DEQ_NOTIF))
     return 0;
   else if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF)
-    return 1;
+    return (svm_fifo_max_enqueue (f) >= f->shr->deq_thresh);
   if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL)
     {
       u32 max_deq = svm_fifo_max_dequeue_cons (f);
@@ -846,12 +843,6 @@ svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
       if (!f->shr->has_deq_ntf && svm_fifo_is_empty (f))
 	return 1;
     }
-  if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH)
-    {
-      if (!f->shr->has_deq_ntf &&
-	  (svm_fifo_max_dequeue (f) <= f->shr->deq_thresh))
-	return 1;
-    }
   return 0;
 }
 
@@ -859,7 +850,7 @@ svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
  * Set the fifo dequeue threshold which will be used for notifications.
  *
  * Note: If not set, by default threshold is zero, equivalent to
- * empty.
+ * generating notification on each dequeue event.
  */
 static inline void
 svm_fifo_set_deq_thresh (svm_fifo_t *f, u32 thresh)