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authorEdward Cree <ecree@solarflare.com>2020-09-03 22:34:57 +0100
committerJakub Kicinski <kuba@kernel.org>2020-09-05 12:21:40 -0700
commit5374d6024cd47e028f96a382104b2653f010b430 (patch)
tree0ef043f9bf31093acc8660897bb0a258628c7e3d /drivers/net/ethernet/sfc
parent8cb2675634ab8ec7986aa9dfe1a7a934872ef51d (diff)
sfc: use tx_queue->old_read_count in EF100 TX path
As in the Siena/EF10 case, it minimises cacheline ping-pong between the TX and completion paths. Signed-off-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers/net/ethernet/sfc')
-rw-r--r--drivers/net/ethernet/sfc/ef100_tx.c8
-rw-r--r--drivers/net/ethernet/sfc/net_driver.h14
2 files changed, 20 insertions, 2 deletions
diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
index ce1b462efd17..078c7ec2a70e 100644
--- a/drivers/net/ethernet/sfc/ef100_tx.c
+++ b/drivers/net/ethernet/sfc/ef100_tx.c
@@ -360,15 +360,19 @@ int ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
goto err;
ef100_tx_make_descriptors(tx_queue, skb, segments);
- fill_level = efx_channel_tx_fill_level(tx_queue->channel);
+ fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
if (fill_level > efx->txq_stop_thresh) {
+ struct efx_tx_queue *txq2;
+
netif_tx_stop_queue(tx_queue->core_txq);
/* Re-read after a memory barrier in case we've raced with
* the completion path. Otherwise there's a danger we'll never
* restart the queue if all completions have just happened.
*/
smp_mb();
- fill_level = efx_channel_tx_fill_level(tx_queue->channel);
+ efx_for_each_channel_tx_queue(txq2, tx_queue->channel)
+ txq2->old_read_count = READ_ONCE(txq2->read_count);
+ fill_level = efx_channel_tx_old_fill_level(tx_queue->channel);
if (fill_level < efx->txq_stop_thresh)
netif_tx_start_queue(tx_queue->core_txq);
}
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index adc138f9d15f..366e649fa869 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -1692,6 +1692,20 @@ efx_channel_tx_fill_level(struct efx_channel *channel)
return fill_level;
}
+/* Conservative approximation of efx_channel_tx_fill_level using cached value */
+static inline unsigned int
+efx_channel_tx_old_fill_level(struct efx_channel *channel)
+{
+ struct efx_tx_queue *tx_queue;
+ unsigned int fill_level = 0;
+
+ efx_for_each_channel_tx_queue(tx_queue, channel)
+ fill_level = max(fill_level,
+ tx_queue->insert_count - tx_queue->old_read_count);
+
+ return fill_level;
+}
+
/* Get all supported features.
* If a feature is not fixed, it is present in hw_features.
* If a feature is fixed, it does not present in hw_features, but