diff options
Diffstat (limited to 'drivers/net/ethernet/sfc/tx.c')
| -rw-r--r-- | drivers/net/ethernet/sfc/tx.c | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c index b868920b680c..48d91b26f1a2 100644 --- a/drivers/net/ethernet/sfc/tx.c +++ b/drivers/net/ethernet/sfc/tx.c @@ -264,6 +264,30 @@ static int efx_enqueue_skb_pio(struct efx_tx_queue *tx_queue, ++tx_queue->insert_count; return 0; } + +/* Decide whether we can use TX PIO, ie. write packet data directly into + * a buffer on the device. This can reduce latency at the expense of + * throughput, so we only do this if both hardware and software TX rings + * are empty, including all queues for the channel. This also ensures that + * only one packet at a time can be using the PIO buffer. If the xmit_more + * flag is set then we don't use this - there'll be another packet along + * shortly and we want to hold off the doorbell. + */ +static bool efx_tx_may_pio(struct efx_tx_queue *tx_queue) +{ + struct efx_channel *channel = tx_queue->channel; + + if (!tx_queue->piobuf) + return false; + + EFX_WARN_ON_ONCE_PARANOID(!channel->efx->type->option_descriptors); + + efx_for_each_channel_tx_queue(tx_queue, channel) + if (!efx_nic_tx_is_empty(tx_queue, tx_queue->packet_write_count)) + return false; + + return true; +} #endif /* EFX_USE_PIO */ /* Send any pending traffic for a channel. xmit_more is shared across all @@ -326,7 +350,7 @@ netdev_tx_t __efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb goto err; #ifdef EFX_USE_PIO } else if (skb_len <= efx_piobuf_size && !xmit_more && - efx_nic_may_tx_pio(tx_queue)) { + efx_tx_may_pio(tx_queue)) { /* Use PIO for short packets with an empty queue. */ if (efx_enqueue_skb_pio(tx_queue, skb)) goto err; |