[PATCH v3 net-next 2/2] ibmvnic: Use ndo_get_stats64 to fix inaccurate SAR reporting

[PATCH v3 net-next 2/2] ibmvnic: Use ndo_get_stats64 to fix inaccurate SAR reporting

[Mingming Cao]

VNIC testing on multi-core Power systems showed SAR stats drift
and packet rate inconsistencies under load.

Implements ndo_get_stats64 to provide safe aggregation of queue-level
atomic64 counters into rtnl_link_stats64 for use by tools like 'ip -s',
'ifconfig', and 'sar'. Switch to ndo_get_stats64 to align SAR reporting
with the standard kernel interface for retrieving netdev stats.

This removes redundant per-adapter stat updates, reduces overhead,
eliminates cacheline bouncing from hot path updates, and improves
the accuracy of reported packet rates.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed by: Brian King <bjking1@linux.ibm.com>
Reviewed by: Dave Marquardt <davemarq@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 79fdba4293a4..6dd7809b1bc7 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2312,8 +2312,6 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 					  tx_pool->num_buffers - 1 :
 					  tx_pool->consumer_index - 1;
 		tx_buff = &tx_pool->tx_buff[index];
-		adapter->netdev->stats.tx_packets--;
-		adapter->netdev->stats.tx_bytes -= tx_buff->skb->len;
 		atomic64_dec(&adapter->tx_stats_buffers[queue_num].batched_packets);
 		if (atomic64_sub_return(tx_buff->skb->len,
 					&adapter->tx_stats_buffers[queue_num].bytes) < 0) {
@@ -2325,9 +2323,9 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 				    atomic64_read(&adapter->tx_stats_buffers[queue_num].bytes),
 				    tx_buff->skb->len);
 		}
+		atomic64_inc(&adapter->tx_stats_buffers[queue_num].dropped_packets);
 		dev_kfree_skb_any(tx_buff->skb);
 		tx_buff->skb = NULL;
-		adapter->netdev->stats.tx_dropped++;
 	}
 
 	ind_bufp->index = 0;
@@ -2655,9 +2653,6 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	}
 out:
 	rcu_read_unlock();
-	netdev->stats.tx_dropped += tx_dropped;
-	netdev->stats.tx_bytes += tx_bytes;
-	netdev->stats.tx_packets += tx_bpackets + tx_dpackets;
 	adapter->tx_send_failed += tx_send_failed;
 	adapter->tx_map_failed += tx_map_failed;
 	atomic64_add(tx_bpackets, &adapter->tx_stats_buffers[queue_num].batched_packets);
@@ -3460,6 +3455,25 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 	return -ret;
 }
 
+static void ibmvnic_get_stats64(struct net_device *netdev,
+				struct rtnl_link_stats64 *stats)
+{
+	struct ibmvnic_adapter *adapter = netdev_priv(netdev);
+	int i;
+
+	for (i = 0; i < adapter->req_rx_queues; i++) {
+		stats->rx_packets += atomic64_read(&adapter->rx_stats_buffers[i].packets);
+		stats->rx_bytes   += atomic64_read(&adapter->rx_stats_buffers[i].bytes);
+	}
+
+	for (i = 0; i < adapter->req_tx_queues; i++) {
+		stats->tx_packets += atomic64_read(&adapter->tx_stats_buffers[i].batched_packets);
+		stats->tx_packets += atomic64_read(&adapter->tx_stats_buffers[i].direct_packets);
+		stats->tx_bytes   += atomic64_read(&adapter->tx_stats_buffers[i].bytes);
+		stats->tx_dropped += atomic64_read(&adapter->tx_stats_buffers[i].dropped_packets);
+	}
+}
+
 static void ibmvnic_tx_timeout(struct net_device *dev, unsigned int txqueue)
 {
 	struct ibmvnic_adapter *adapter = netdev_priv(dev);
@@ -3575,8 +3589,6 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 
 		length = skb->len;
 		napi_gro_receive(napi, skb); /* send it up */
-		netdev->stats.rx_packets++;
-		netdev->stats.rx_bytes += length;
 		atomic64_inc(&adapter->rx_stats_buffers[scrq_num].packets);
 		atomic64_add(length, &adapter->rx_stats_buffers[scrq_num].bytes);
 		frames_processed++;
@@ -3686,6 +3698,7 @@ static const struct net_device_ops ibmvnic_netdev_ops = {
 	.ndo_set_rx_mode	= ibmvnic_set_multi,
 	.ndo_set_mac_address	= ibmvnic_set_mac,
 	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_get_stats64	= ibmvnic_get_stats64,
 	.ndo_tx_timeout		= ibmvnic_tx_timeout,
 	.ndo_change_mtu		= ibmvnic_change_mtu,
 	.ndo_features_check     = ibmvnic_features_check,
-- 
2.39.3 (Apple Git-146)

[PATCH v3 net-next resubmit 0/2] ibmvnic: Fix/Improve queue stats

[Mingming Cao]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=true, Size: 2545 bytes --]

This series is resubmitted after the bug fix for hardcoded 
`NUM_RX_STATS` and `NUM_TX_STATS` has already been included in the `net-next` tree.

This patch series introduces two updates to the ibmvnic driver, 
focusing on improving the accuracy and safety of queue-level statistics.

Patch 1: Convert per-queue RX/TX stats to atomic64_t to ensure thread-safe 
updates in concurrent environments. This establishes a safe and consistent 
foundation for subsequent statistics-related fixes. 

Patch 2: Fix inaccurate sar statistics by implementing ndo_get_stats64() and 
removing the outdated manual updates to netdev->stats. This patch also improves
packets rates and bandwith with large workload.


--------------------------------------

Changes since v2:
link to v2: https://www.spinics.net/lists/netdev/msg1104665.html

- Dropped Patch 2 from v2, which fixed the hardcoded `NUM_RX_STATS` and `NUM_TX_STATS`,
 as suggested by Simon. https://www.spinics.net/lists/netdev/msg1106669.html included
 in net-next
- Updated Patch 1 in v2 to rebase on top of the above fix in `net`.
– Patch 3 in v2 (now patch 2) unchanged.
- Dropped Patch 4 from v2, which raised the default number of indirect sub-CRQ entries 
and introduced a module parameter for backward compatibility. Based on review feedback, 
plan to explore alternative ways to handle older systems without adding a module parameter.

---

Changes since v1:
 Link to v1: https://www.spinics.net/lists/netdev/msg1103893.html

Patch 1 (was Patch 2 in v1): Introduces atomic64_t stats early to establish 
a consistent foundation. Replaces atomic64_sub() with atomic64_sub_return() 
and adds a warning for underflow. This change now comes first to ensure correct
 ordering of dependency with stat size derivation.

Patch 2 (was Patch 1 in v1): Commit message rewritten to clearly highlight the 
mismatch bug caused by static stat counts and rebased on top of the atomic64 
conversion to avoid broken logic during intermediate states.

Patch 3: No functional changes

Patch 4: Commit message clarified to explain the use of 128 indirect entries 
on POWER9+ systems and the intent of the module parameter as a transitional 
fallback for legacy or constrained systems.

Mingming Cao (2):
  ibmvnic: Use atomic64_t for queue stats
  ibmvnic: Use ndo_get_stats64 to fix inaccurate SAR reporting

 drivers/net/ethernet/ibm/ibmvnic.c | 71 +++++++++++++++++++-----------
 drivers/net/ethernet/ibm/ibmvnic.h | 18 ++++----
 2 files changed, 55 insertions(+), 34 deletions(-)

-- 
2.39.3 (Apple Git-146)

[PATCH v3 net-next 1/2] ibmvnic: Use atomic64_t for queue stats

[Mingming Cao]

This patch improves the ibmvnic driver by changing the per-queue
packet and byte counters to atomic64_t types. This makes updates
thread-safe and easier to manage across multiple cores.

It also updates the ethtool statistics to safely read these new counters.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed-by: Brian King <bjking1@linux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
Reviewed by: Rick Lindsley <ricklind@linux.ibm.com>
Reviewed by: Haren Myneni <haren@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 42 ++++++++++++++++++------------
 drivers/net/ethernet/ibm/ibmvnic.h | 18 ++++++-------
 2 files changed, 34 insertions(+), 26 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 92647e137cf8..79fdba4293a4 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2314,9 +2314,17 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 		tx_buff = &tx_pool->tx_buff[index];
 		adapter->netdev->stats.tx_packets--;
 		adapter->netdev->stats.tx_bytes -= tx_buff->skb->len;
-		adapter->tx_stats_buffers[queue_num].batched_packets--;
-		adapter->tx_stats_buffers[queue_num].bytes -=
-						tx_buff->skb->len;
+		atomic64_dec(&adapter->tx_stats_buffers[queue_num].batched_packets);
+		if (atomic64_sub_return(tx_buff->skb->len,
+					&adapter->tx_stats_buffers[queue_num].bytes) < 0) {
+			atomic64_set(&adapter->tx_stats_buffers[queue_num].bytes, 0);
+			netdev_warn(adapter->netdev,
+				    "TX stats underflow on queue %u: bytes (%lld) < skb->len (%u),\n"
+				    "clamping to 0\n",
+				    queue_num,
+				    atomic64_read(&adapter->tx_stats_buffers[queue_num].bytes),
+				    tx_buff->skb->len);
+		}
 		dev_kfree_skb_any(tx_buff->skb);
 		tx_buff->skb = NULL;
 		adapter->netdev->stats.tx_dropped++;
@@ -2652,10 +2660,10 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	netdev->stats.tx_packets += tx_bpackets + tx_dpackets;
 	adapter->tx_send_failed += tx_send_failed;
 	adapter->tx_map_failed += tx_map_failed;
-	adapter->tx_stats_buffers[queue_num].batched_packets += tx_bpackets;
-	adapter->tx_stats_buffers[queue_num].direct_packets += tx_dpackets;
-	adapter->tx_stats_buffers[queue_num].bytes += tx_bytes;
-	adapter->tx_stats_buffers[queue_num].dropped_packets += tx_dropped;
+	atomic64_add(tx_bpackets, &adapter->tx_stats_buffers[queue_num].batched_packets);
+	atomic64_add(tx_dpackets, &adapter->tx_stats_buffers[queue_num].direct_packets);
+	atomic64_add(tx_bytes, &adapter->tx_stats_buffers[queue_num].bytes);
+	atomic64_add(tx_dropped, &adapter->tx_stats_buffers[queue_num].dropped_packets);
 
 	return ret;
 }
@@ -3569,8 +3577,8 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 		napi_gro_receive(napi, skb); /* send it up */
 		netdev->stats.rx_packets++;
 		netdev->stats.rx_bytes += length;
-		adapter->rx_stats_buffers[scrq_num].packets++;
-		adapter->rx_stats_buffers[scrq_num].bytes += length;
+		atomic64_inc(&adapter->rx_stats_buffers[scrq_num].packets);
+		atomic64_add(length, &adapter->rx_stats_buffers[scrq_num].bytes);
 		frames_processed++;
 	}
 
@@ -3874,22 +3882,22 @@ static void ibmvnic_get_ethtool_stats(struct net_device *dev,
 				      (adapter, ibmvnic_stats[i].offset));
 
 	for (j = 0; j < adapter->req_tx_queues; j++) {
-		data[i] = adapter->tx_stats_buffers[j].batched_packets;
+		data[i] = atomic64_read(&adapter->tx_stats_buffers[j].batched_packets);
 		i++;
-		data[i] = adapter->tx_stats_buffers[j].direct_packets;
+		data[i] = atomic64_read(&adapter->tx_stats_buffers[j].direct_packets);
 		i++;
-		data[i] = adapter->tx_stats_buffers[j].bytes;
+		data[i] = atomic64_read(&adapter->tx_stats_buffers[j].bytes);
 		i++;
-		data[i] = adapter->tx_stats_buffers[j].dropped_packets;
+		data[i] = atomic64_read(&adapter->tx_stats_buffers[j].dropped_packets);
 		i++;
 	}
 
 	for (j = 0; j < adapter->req_rx_queues; j++) {
-		data[i] = adapter->rx_stats_buffers[j].packets;
+		data[i] = atomic64_read(&adapter->rx_stats_buffers[j].packets);
 		i++;
-		data[i] = adapter->rx_stats_buffers[j].bytes;
+		data[i] = atomic64_read(&adapter->rx_stats_buffers[j].bytes);
 		i++;
-		data[i] = adapter->rx_stats_buffers[j].interrupts;
+		data[i] = atomic64_read(&adapter->rx_stats_buffers[j].interrupts);
 		i++;
 	}
 }
@@ -4307,7 +4315,7 @@ static irqreturn_t ibmvnic_interrupt_rx(int irq, void *instance)
 	if (unlikely(adapter->state != VNIC_OPEN))
 		return IRQ_NONE;
 
-	adapter->rx_stats_buffers[scrq->scrq_num].interrupts++;
+	atomic64_inc(&adapter->rx_stats_buffers[scrq->scrq_num].interrupts);
 
 	if (napi_schedule_prep(&adapter->napi[scrq->scrq_num])) {
 		disable_scrq_irq(adapter, scrq);
diff --git a/drivers/net/ethernet/ibm/ibmvnic.h b/drivers/net/ethernet/ibm/ibmvnic.h
index 246ddce753f9..e574eed97cc0 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.h
+++ b/drivers/net/ethernet/ibm/ibmvnic.h
@@ -212,23 +212,23 @@ struct ibmvnic_statistics {
 } __packed __aligned(8);
 
 struct ibmvnic_tx_queue_stats {
-	u64 batched_packets;
-	u64 direct_packets;
-	u64 bytes;
-	u64 dropped_packets;
+	atomic64_t batched_packets;
+	atomic64_t direct_packets;
+	atomic64_t bytes;
+	atomic64_t dropped_packets;
 };
 
 #define NUM_TX_STATS \
-	(sizeof(struct ibmvnic_tx_queue_stats) / sizeof(u64))
+	(sizeof(struct ibmvnic_tx_queue_stats) / sizeof(atomic64_t))
 
 struct ibmvnic_rx_queue_stats {
-	u64 packets;
-	u64 bytes;
-	u64 interrupts;
+	atomic64_t packets;
+	atomic64_t bytes;
+	atomic64_t interrupts;
 };
 
 #define NUM_RX_STATS \
-	(sizeof(struct ibmvnic_rx_queue_stats) / sizeof(u64))
+	(sizeof(struct ibmvnic_rx_queue_stats) / sizeof(atomic64_t))
 
 struct ibmvnic_acl_buffer {
 	__be32 len;
-- 
2.39.3 (Apple Git-146)

[PATCH v3 net-next 2/2] ibmvnic: Use ndo_get_stats64 to fix inaccurate SAR reporting

[Mingming Cao]

VNIC testing on multi-core Power systems showed SAR stats drift
and packet rate inconsistencies under load.

Implements ndo_get_stats64 to provide safe aggregation of queue-level
atomic64 counters into rtnl_link_stats64 for use by tools like 'ip -s',
'ifconfig', and 'sar'. Switch to ndo_get_stats64 to align SAR reporting
with the standard kernel interface for retrieving netdev stats.

This removes redundant per-adapter stat updates, reduces overhead,
eliminates cacheline bouncing from hot path updates, and improves
the accuracy of reported packet rates.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed by: Brian King <bjking1@linux.ibm.com>
Reviewed by: Dave Marquardt <davemarq@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 79fdba4293a4..6dd7809b1bc7 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2312,8 +2312,6 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 					  tx_pool->num_buffers - 1 :
 					  tx_pool->consumer_index - 1;
 		tx_buff = &tx_pool->tx_buff[index];
-		adapter->netdev->stats.tx_packets--;
-		adapter->netdev->stats.tx_bytes -= tx_buff->skb->len;
 		atomic64_dec(&adapter->tx_stats_buffers[queue_num].batched_packets);
 		if (atomic64_sub_return(tx_buff->skb->len,
 					&adapter->tx_stats_buffers[queue_num].bytes) < 0) {
@@ -2325,9 +2323,9 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
 				    atomic64_read(&adapter->tx_stats_buffers[queue_num].bytes),
 				    tx_buff->skb->len);
 		}
+		atomic64_inc(&adapter->tx_stats_buffers[queue_num].dropped_packets);
 		dev_kfree_skb_any(tx_buff->skb);
 		tx_buff->skb = NULL;
-		adapter->netdev->stats.tx_dropped++;
 	}
 
 	ind_bufp->index = 0;
@@ -2655,9 +2653,6 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	}
 out:
 	rcu_read_unlock();
-	netdev->stats.tx_dropped += tx_dropped;
-	netdev->stats.tx_bytes += tx_bytes;
-	netdev->stats.tx_packets += tx_bpackets + tx_dpackets;
 	adapter->tx_send_failed += tx_send_failed;
 	adapter->tx_map_failed += tx_map_failed;
 	atomic64_add(tx_bpackets, &adapter->tx_stats_buffers[queue_num].batched_packets);
@@ -3460,6 +3455,25 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 	return -ret;
 }
 
+static void ibmvnic_get_stats64(struct net_device *netdev,
+				struct rtnl_link_stats64 *stats)
+{
+	struct ibmvnic_adapter *adapter = netdev_priv(netdev);
+	int i;
+
+	for (i = 0; i < adapter->req_rx_queues; i++) {
+		stats->rx_packets += atomic64_read(&adapter->rx_stats_buffers[i].packets);
+		stats->rx_bytes   += atomic64_read(&adapter->rx_stats_buffers[i].bytes);
+	}
+
+	for (i = 0; i < adapter->req_tx_queues; i++) {
+		stats->tx_packets += atomic64_read(&adapter->tx_stats_buffers[i].batched_packets);
+		stats->tx_packets += atomic64_read(&adapter->tx_stats_buffers[i].direct_packets);
+		stats->tx_bytes   += atomic64_read(&adapter->tx_stats_buffers[i].bytes);
+		stats->tx_dropped += atomic64_read(&adapter->tx_stats_buffers[i].dropped_packets);
+	}
+}
+
 static void ibmvnic_tx_timeout(struct net_device *dev, unsigned int txqueue)
 {
 	struct ibmvnic_adapter *adapter = netdev_priv(dev);
@@ -3575,8 +3589,6 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget)
 
 		length = skb->len;
 		napi_gro_receive(napi, skb); /* send it up */
-		netdev->stats.rx_packets++;
-		netdev->stats.rx_bytes += length;
 		atomic64_inc(&adapter->rx_stats_buffers[scrq_num].packets);
 		atomic64_add(length, &adapter->rx_stats_buffers[scrq_num].bytes);
 		frames_processed++;
@@ -3686,6 +3698,7 @@ static const struct net_device_ops ibmvnic_netdev_ops = {
 	.ndo_set_rx_mode	= ibmvnic_set_multi,
 	.ndo_set_mac_address	= ibmvnic_set_mac,
 	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_get_stats64	= ibmvnic_get_stats64,
 	.ndo_tx_timeout		= ibmvnic_tx_timeout,
 	.ndo_change_mtu		= ibmvnic_change_mtu,
 	.ndo_features_check     = ibmvnic_features_check,
-- 
2.39.3 (Apple Git-146)

Re: [PATCH v3 net-next 1/2] ibmvnic: Use atomic64_t for queue stats

[Simon Horman]

On Mon, Jul 14, 2025 at 01:35:06PM -0400, Mingming Cao wrote:
> This patch improves the ibmvnic driver by changing the per-queue
> packet and byte counters to atomic64_t types. This makes updates
> thread-safe and easier to manage across multiple cores.
> 
> It also updates the ethtool statistics to safely read these new counters.
> 
> Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
> Reviewed-by: Brian King <bjking1@linux.ibm.com>
> Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
> Reviewed by: Rick Lindsley <ricklind@linux.ibm.com>
> Reviewed by: Haren Myneni <haren@linux.ibm.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH v3 net-next 2/2] ibmvnic: Use ndo_get_stats64 to fix inaccurate SAR reporting

[Simon Horman]

On Mon, Jul 14, 2025 at 01:35:07PM -0400, Mingming Cao wrote:
> VNIC testing on multi-core Power systems showed SAR stats drift
> and packet rate inconsistencies under load.
> 
> Implements ndo_get_stats64 to provide safe aggregation of queue-level
> atomic64 counters into rtnl_link_stats64 for use by tools like 'ip -s',
> 'ifconfig', and 'sar'. Switch to ndo_get_stats64 to align SAR reporting
> with the standard kernel interface for retrieving netdev stats.
> 
> This removes redundant per-adapter stat updates, reduces overhead,
> eliminates cacheline bouncing from hot path updates, and improves
> the accuracy of reported packet rates.
> 
> Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
> Reviewed by: Brian King <bjking1@linux.ibm.com>
> Reviewed by: Dave Marquardt <davemarq@linux.ibm.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH v3 net-next 1/2] ibmvnic: Use atomic64_t for queue stats

[Jakub Kicinski]

On Mon, 14 Jul 2025 13:35:06 -0400 Mingming Cao wrote:
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 92647e137cf8..79fdba4293a4 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -2314,9 +2314,17 @@ static void ibmvnic_tx_scrq_clean_buffer(struct ibmvnic_adapter *adapter,
>  		tx_buff = &tx_pool->tx_buff[index];
>  		adapter->netdev->stats.tx_packets--;
>  		adapter->netdev->stats.tx_bytes -= tx_buff->skb->len;
> -		adapter->tx_stats_buffers[queue_num].batched_packets--;
> -		adapter->tx_stats_buffers[queue_num].bytes -=
> -						tx_buff->skb->len;
> +		atomic64_dec(&adapter->tx_stats_buffers[queue_num].batched_packets);
> +		if (atomic64_sub_return(tx_buff->skb->len,
> +					&adapter->tx_stats_buffers[queue_num].bytes) < 0) {
> +			atomic64_set(&adapter->tx_stats_buffers[queue_num].bytes, 0);
> +			netdev_warn(adapter->netdev,

Any datapath print needs to be rate limited, otherwise it may flood
the logs.

> +				    "TX stats underflow on queue %u: bytes (%lld) < skb->len (%u),\n"
> +				    "clamping to 0\n",
> +				    queue_num,
> +				    atomic64_read(&adapter->tx_stats_buffers[queue_num].bytes),
> +				    tx_buff->skb->len);
> +		}
>  		dev_kfree_skb_any(tx_buff->skb);
>  		tx_buff->skb = NULL;
>  		adapter->netdev->stats.tx_dropped++;
> @@ -2652,10 +2660,10 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
>  	netdev->stats.tx_packets += tx_bpackets + tx_dpackets;
>  	adapter->tx_send_failed += tx_send_failed;
>  	adapter->tx_map_failed += tx_map_failed;
> -	adapter->tx_stats_buffers[queue_num].batched_packets += tx_bpackets;
> -	adapter->tx_stats_buffers[queue_num].direct_packets += tx_dpackets;
> -	adapter->tx_stats_buffers[queue_num].bytes += tx_bytes;
> -	adapter->tx_stats_buffers[queue_num].dropped_packets += tx_dropped;
> +	atomic64_add(tx_bpackets, &adapter->tx_stats_buffers[queue_num].batched_packets);
> +	atomic64_add(tx_dpackets, &adapter->tx_stats_buffers[queue_num].direct_packets);
> +	atomic64_add(tx_bytes, &adapter->tx_stats_buffers[queue_num].bytes);
> +	atomic64_add(tx_dropped, &adapter->tx_stats_buffers[queue_num].dropped_packets);

Are atomics really cheap on your platform? Normally having these many
atomic ops per packet would bring performance concerns.
I assume queue accesses are already protected by some sort of a lock
so isn't it enough to make the stats per queue without making them
atomic?
-- 
pw-bot: cr