buffers: performance improvement

Initialize the local variables as to prevent first fall
through one by one processing; skip prefetching rather
than doing one by one when count below 12.

Type: improvement

Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
Change-Id: If02935da081e24f7cfe408811ccf6922cf982092

1 files changed, 21 insertions, 7 deletions

diff --git a/src/vlib/buffer_funcs.h b/src/vlib/buffer_funcs.h
index 95b622c202c..f1be94c61f4 100644
--- a/src/vlib/buffer_funcs.h
+++ b/src/vlib/buffer_funcs.h
@@ -786,28 +786,42 @@ vlib_buffer_free_inline (vlib_main_t * vm, u32 * buffers, u32 n_buffers,
   vlib_buffer_t bt = { };
 #if defined(CLIB_HAVE_VEC128)
   vlib_buffer_t bpi_mask = {.buffer_pool_index = ~0 };
-  vlib_buffer_t bpi_vec = {.buffer_pool_index = ~0 };
+  vlib_buffer_t bpi_vec = {};
   vlib_buffer_t flags_refs_mask = {
     .flags = VLIB_BUFFER_NEXT_PRESENT,
     .ref_count = ~1
   };
 #endif
 
+  if (PREDICT_FALSE (n_buffers == 0))
+    return;
+
+  vlib_buffer_t *b = vlib_get_buffer (vm, buffers[0]);
+  buffer_pool_index = b->buffer_pool_index;
+  bp = vlib_get_buffer_pool (vm, buffer_pool_index);
+  vlib_buffer_copy_template (&bt, &bp->buffer_template);
+#if defined(CLIB_HAVE_VEC128)
+  bpi_vec.buffer_pool_index = buffer_pool_index;
+#endif
+
   while (n_buffers)
     {
       vlib_buffer_t *b[8];
       u32 bi, sum = 0, flags, next;
 
-      if (n_buffers < 12)
+      if (n_buffers < 4)
 	goto one_by_one;
 
       vlib_get_buffers (vm, buffers, b, 4);
-      vlib_get_buffers (vm, buffers + 8, b + 4, 4);
 
-      vlib_prefetch_buffer_header (b[4], LOAD);
-      vlib_prefetch_buffer_header (b[5], LOAD);
-      vlib_prefetch_buffer_header (b[6], LOAD);
-      vlib_prefetch_buffer_header (b[7], LOAD);
+      if (n_buffers >= 12)
+	{
+	  vlib_get_buffers (vm, buffers + 8, b + 4, 4);
+	  vlib_prefetch_buffer_header (b[4], LOAD);
+	  vlib_prefetch_buffer_header (b[5], LOAD);
+	  vlib_prefetch_buffer_header (b[6], LOAD);
+	  vlib_prefetch_buffer_header (b[7], LOAD);
+	}
 
 #if defined(CLIB_HAVE_VEC128)
       u8x16 p0, p1, p2, p3, r;