netdev - [net-next 13/15] i40evf: fix ring to vector mapping

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Date:   Fri, 29 Sep 2017 17:45:05 -0700
From:   Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:     davem@...emloft.net
Cc:     Alan Brady <alan.brady@...el.com>, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: [net-next 13/15] i40evf: fix ring to vector mapping

From: Alan Brady <alan.brady@...el.com>

The current implementation for mapping queues to vectors is broken
because it attempts to map each Tx and Rx ring to its own vector,
however we use combined queues so we should actually be mapping the
Tx/Rx rings together on one vector.

Also in the current implementation, in the case where we have more
queues than vectors, we attempt to group the queues together into
'chunks' and map each 'chunk' of queues to a vector.  Chunking them
together would be more ideal if, and only if, we only had RSS because of
the way the hashing algorithm works but in the case of a future patch
that enables VF ADq, round robin assignment is better and still works
with RSS.

This patch resolves both those issues and simplifies the code needed to
accomplish this.  Instead of treating the case where we have more queues
than vectors as special, if we notice our vector index is greater than
vectors, reset the vector index to zero and continue mapping.  This
should ensure that in both cases, whether we have enough vectors for
each queue or not, the queues get appropriately mapped.

Signed-off-by: Alan Brady <alan.brady@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
---
 drivers/net/ethernet/intel/i40evf/i40evf_main.c | 48 ++++++-------------------
 1 file changed, 10 insertions(+), 38 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40evf/i40evf_main.c b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
index 80ade6510279..69ef6c1d5364 100644
--- a/drivers/net/ethernet/intel/i40evf/i40evf_main.c
+++ b/drivers/net/ethernet/intel/i40evf/i40evf_main.c
@@ -432,52 +432,24 @@ i40evf_map_vector_to_txq(struct i40evf_adapter *adapter, int v_idx, int t_idx)
  **/
 static int i40evf_map_rings_to_vectors(struct i40evf_adapter *adapter)
 {
+	int rings_remaining = adapter->num_active_queues;
+	int ridx = 0, vidx = 0;
 	int q_vectors;
-	int v_start = 0;
-	int rxr_idx = 0, txr_idx = 0;
-	int rxr_remaining = adapter->num_active_queues;
-	int txr_remaining = adapter->num_active_queues;
-	int i, j;
-	int rqpv, tqpv;
 	int err = 0;
 
 	q_vectors = adapter->num_msix_vectors - NONQ_VECS;
 
-	/* The ideal configuration...
-	 * We have enough vectors to map one per queue.
-	 */
-	if (q_vectors >= (rxr_remaining * 2)) {
-		for (; rxr_idx < rxr_remaining; v_start++, rxr_idx++)
-			i40evf_map_vector_to_rxq(adapter, v_start, rxr_idx);
+	for (; ridx < rings_remaining; ridx++) {
+		i40evf_map_vector_to_rxq(adapter, vidx, ridx);
+		i40evf_map_vector_to_txq(adapter, vidx, ridx);
 
-		for (; txr_idx < txr_remaining; v_start++, txr_idx++)
-			i40evf_map_vector_to_txq(adapter, v_start, txr_idx);
-		goto out;
-	}
-
-	/* If we don't have enough vectors for a 1-to-1
-	 * mapping, we'll have to group them so there are
-	 * multiple queues per vector.
-	 * Re-adjusting *qpv takes care of the remainder.
-	 */
-	for (i = v_start; i < q_vectors; i++) {
-		rqpv = DIV_ROUND_UP(rxr_remaining, q_vectors - i);
-		for (j = 0; j < rqpv; j++) {
-			i40evf_map_vector_to_rxq(adapter, i, rxr_idx);
-			rxr_idx++;
-			rxr_remaining--;
-		}
-	}
-	for (i = v_start; i < q_vectors; i++) {
-		tqpv = DIV_ROUND_UP(txr_remaining, q_vectors - i);
-		for (j = 0; j < tqpv; j++) {
-			i40evf_map_vector_to_txq(adapter, i, txr_idx);
-			txr_idx++;
-			txr_remaining--;
-		}
+		/* In the case where we have more queues than vectors, continue
+		 * round-robin on vectors until all queues are mapped.
+		 */
+		if (++vidx >= q_vectors)
+			vidx = 0;
 	}
 
-out:
 	adapter->aq_required |= I40EVF_FLAG_AQ_MAP_VECTORS;
 
 	return err;
-- 
2.14.1