netdev - [PATCH net-next 09/12] ibmvnic: Ensure that device queue memory is cache-line aligned

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Date:   Thu, 12 Nov 2020 13:10:04 -0600
From:   Thomas Falcon <tlfalcon@...ux.ibm.com>
To:     netdev@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, dnbanerg@...ibm.com,
        brking@...ux.vnet.ibm.com, pradeep@...ibm.com,
        drt@...ux.vnet.ibm.com, sukadev@...ux.vnet.ibm.com,
        ljp@...ux.vnet.ibm.com, cforno12@...ux.ibm.com,
        tlfalcon@...ux.ibm.com, ricklind@...ux.ibm.com
Subject: [PATCH net-next 09/12] ibmvnic: Ensure that device queue memory is cache-line aligned

From: "Dwip N. Banerjee" <dnbanerg@...ibm.com>

PCI bus slowdowns were observed on IBM VNIC devices as a result
of partial cache line writes and non-cache aligned full cache line writes.
Ensure that packet data buffers are cache-line aligned to avoid these
slowdowns.

Signed-off-by: Dwip N. Banerjee <dnbanerg@...ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c |  9 ++++++---
 drivers/net/ethernet/ibm/ibmvnic.h | 10 +++++-----
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index b2ca34e94078..dc42bdc6d3e1 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -498,7 +498,7 @@ static int reset_rx_pools(struct ibmvnic_adapter *adapter)
 
 		if (rx_pool->buff_size != buff_size) {
 			free_long_term_buff(adapter, &rx_pool->long_term_buff);
-			rx_pool->buff_size = buff_size;
+			rx_pool->buff_size = ALIGN(buff_size, L1_CACHE_BYTES);
 			rc = alloc_long_term_buff(adapter,
 						  &rx_pool->long_term_buff,
 						  rx_pool->size *
@@ -592,7 +592,7 @@ static int init_rx_pools(struct net_device *netdev)
 
 		rx_pool->size = adapter->req_rx_add_entries_per_subcrq;
 		rx_pool->index = i;
-		rx_pool->buff_size = buff_size;
+		rx_pool->buff_size = ALIGN(buff_size, L1_CACHE_BYTES);
 		rx_pool->active = 1;
 
 		rx_pool->free_map = kcalloc(rx_pool->size, sizeof(int),
@@ -745,6 +745,7 @@ static int init_tx_pools(struct net_device *netdev)
 {
 	struct ibmvnic_adapter *adapter = netdev_priv(netdev);
 	int tx_subcrqs;
+	u64 buff_size;
 	int i, rc;
 
 	tx_subcrqs = adapter->num_active_tx_scrqs;
@@ -761,9 +762,11 @@ static int init_tx_pools(struct net_device *netdev)
 	adapter->num_active_tx_pools = tx_subcrqs;
 
 	for (i = 0; i < tx_subcrqs; i++) {
+		buff_size = adapter->req_mtu + VLAN_HLEN;
+		buff_size = ALIGN(buff_size, L1_CACHE_BYTES);
 		rc = init_one_tx_pool(netdev, &adapter->tx_pool[i],
 				      adapter->req_tx_entries_per_subcrq,
-				      adapter->req_mtu + VLAN_HLEN);
+				      buff_size);
 		if (rc) {
 			release_tx_pools(adapter);
 			return rc;
diff --git a/drivers/net/ethernet/ibm/ibmvnic.h b/drivers/net/ethernet/ibm/ibmvnic.h
index c6f1842d2023..1e4c7702402b 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.h
+++ b/drivers/net/ethernet/ibm/ibmvnic.h
@@ -884,7 +884,7 @@ struct ibmvnic_sub_crq_queue {
 	atomic_t used;
 	char name[32];
 	u64 handle;
-};
+} ____cacheline_aligned;
 
 struct ibmvnic_long_term_buff {
 	unsigned char *buff;
@@ -908,7 +908,7 @@ struct ibmvnic_tx_pool {
 	struct ibmvnic_long_term_buff long_term_buff;
 	int num_buffers;
 	int buf_size;
-};
+} ____cacheline_aligned;
 
 struct ibmvnic_rx_buff {
 	struct sk_buff *skb;
@@ -929,7 +929,7 @@ struct ibmvnic_rx_pool {
 	int next_alloc;
 	int active;
 	struct ibmvnic_long_term_buff long_term_buff;
-};
+} ____cacheline_aligned;
 
 struct ibmvnic_vpd {
 	unsigned char *buff;
@@ -1014,8 +1014,8 @@ struct ibmvnic_adapter {
 	atomic_t running_cap_crqs;
 	bool wait_capability;
 
-	struct ibmvnic_sub_crq_queue **tx_scrq;
-	struct ibmvnic_sub_crq_queue **rx_scrq;
+	struct ibmvnic_sub_crq_queue **tx_scrq ____cacheline_aligned;
+	struct ibmvnic_sub_crq_queue **rx_scrq ____cacheline_aligned;
 
 	/* rx structs */
 	struct napi_struct *napi;
-- 
2.26.2