i40e: Add a stat for tracking pages waived

In some cases, pages can not be reused because they are not associated with
the correct NUMA zone. Knowing how often pages are waived helps users to
understand the interaction between the driver's memory usage and their
system.

Pass rx_stats through to i40e_can_reuse_rx_page to allow tracking when
pages are waived.

The page waive count is accessible via ethtool.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e.h

@@ -856,6 +856,7 @@ struct i40e_vsi {
 	u64 rx_page_failed;
 	u64 rx_page_reuse;
 	u64 rx_page_alloc;
+	u64 rx_page_waive;
 
 	/* These are containers of ring pointers, allocated at run-time */
 	struct i40e_ring **rx_rings;

drivers/net/ethernet/intel/i40e/i40e_ethtool.c

@@ -297,6 +297,7 @@ static const struct i40e_stats i40e_gstrings_misc_stats[] = {
 	I40E_VSI_STAT("rx_pg_alloc_fail", rx_page_failed),
 	I40E_VSI_STAT("rx_cache_reuse", rx_page_reuse),
 	I40E_VSI_STAT("rx_cache_alloc", rx_page_alloc),
+	I40E_VSI_STAT("rx_cache_waive", rx_page_waive),
 };
 
 /* These PF_STATs might look like duplicates of some NETDEV_STATs,

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -773,7 +773,7 @@ void i40e_update_veb_stats(struct i40e_veb *veb)
  **/
 static void i40e_update_vsi_stats(struct i40e_vsi *vsi)
 {
-	u64 rx_page, rx_buf, rx_reuse, rx_alloc;
+	u64 rx_page, rx_buf, rx_reuse, rx_alloc, rx_waive;
 	struct i40e_pf *pf = vsi->back;
 	struct rtnl_link_stats64 *ons;
 	struct rtnl_link_stats64 *ns;   /* netdev stats */
@@ -808,6 +808,7 @@ static void i40e_update_vsi_stats(struct i40e_vsi *vsi)
 	rx_buf = 0;
 	rx_reuse = 0;
 	rx_alloc = 0;
+	rx_waive = 0;
 	rcu_read_lock();
 	for (q = 0; q < vsi->num_queue_pairs; q++) {
 		/* locate Tx ring */
@@ -843,6 +844,7 @@ static void i40e_update_vsi_stats(struct i40e_vsi *vsi)
 		rx_page += p->rx_stats.alloc_page_failed;
 		rx_reuse += p->rx_stats.page_reuse_count;
 		rx_alloc += p->rx_stats.page_alloc_count;
+		rx_waive += p->rx_stats.page_waive_count;
 
 		if (i40e_enabled_xdp_vsi(vsi)) {
 			/* locate XDP ring */
@@ -872,6 +874,7 @@ static void i40e_update_vsi_stats(struct i40e_vsi *vsi)
 	vsi->rx_buf_failed = rx_buf;
 	vsi->rx_page_reuse = rx_reuse;
 	vsi->rx_page_alloc = rx_alloc;
+	vsi->rx_page_waive = rx_waive;
 
 	ns->rx_packets = rx_p;
 	ns->rx_bytes = rx_b;

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1982,22 +1982,29 @@ static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb,
 /**
  * i40e_can_reuse_rx_page - Determine if page can be reused for another Rx
  * @rx_buffer: buffer containing the page
+ * @rx_stats: rx stats structure for the rx ring
  * @rx_buffer_pgcnt: buffer page refcount pre xdp_do_redirect() call
  *
  * If page is reusable, we have a green light for calling i40e_reuse_rx_page,
  * which will assign the current buffer to the buffer that next_to_alloc is
  * pointing to; otherwise, the DMA mapping needs to be destroyed and
- * page freed
+ * page freed.
+ *
+ * rx_stats will be updated to indicate if the page was waived because it was
+ * not reusable.
  */
 static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
+				   struct i40e_rx_queue_stats *rx_stats,
 				   int rx_buffer_pgcnt)
 {
 	unsigned int pagecnt_bias = rx_buffer->pagecnt_bias;
 	struct page *page = rx_buffer->page;
 
 	/* Is any reuse possible? */
-	if (!dev_page_is_reusable(page))
+	if (!dev_page_is_reusable(page)) {
+		rx_stats->page_waive_count++;
 		return false;
+	}
 
 #if (PAGE_SIZE < 8192)
 	/* if we are only owner of page we can reuse it */
@@ -2237,7 +2244,7 @@ static void i40e_put_rx_buffer(struct i40e_ring *rx_ring,
 			       struct i40e_rx_buffer *rx_buffer,
 			       int rx_buffer_pgcnt)
 {
-	if (i40e_can_reuse_rx_page(rx_buffer, rx_buffer_pgcnt)) {
+	if (i40e_can_reuse_rx_page(rx_buffer, &rx_ring->rx_stats, rx_buffer_pgcnt)) {
 		/* hand second half of page back to the ring */
 		i40e_reuse_rx_page(rx_ring, rx_buffer);
 	} else {

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -299,6 +299,7 @@ struct i40e_rx_queue_stats {
 	u64 alloc_buff_failed;
 	u64 page_reuse_count;
 	u64 page_alloc_count;
+	u64 page_waive_count;
 };
 
 enum i40e_ring_state_t {