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sfc: rewrite efx_tx_may_pio 

Use efx_for_each_channel_tx_queue() rather than efx_tx_queue_partner().
Make some related simplifications of efx_nic_tx_is_empty() to remove
 entry points that aren't used.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Edward Cree 2020-09-03 22:35:29 +01:00 committed by Jakub Kicinski
parent 0d8c122907
commit 8be41842c5
2 changed files with 27 additions and 29 deletions
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30
drivers/net/ethernet/sfc/nic_common.h
View File

@ -65,8 +65,7 @@ efx_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index)
/* Report whether this TX queue would be empty for the given write_count.
* May return false negative.
*/
static inline bool __efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue,
unsigned int write_count)
static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue, unsigned int write_count)
{
unsigned int empty_read_count = READ_ONCE(tx_queue->empty_read_count);
@ -76,17 +75,6 @@ static inline bool __efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue,
return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0;
}
/* Report whether the NIC considers this TX queue empty, using
* packet_write_count (the write count recorded for the last completable
* doorbell push). May return false negative. EF10 only, which is OK
* because only EF10 supports PIO.
*/
static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue)
{
EFX_WARN_ON_ONCE_PARANOID(!tx_queue->efx->type->option_descriptors);
return __efx_nic_tx_is_empty(tx_queue, tx_queue->packet_write_count);
}
/* Get partner of a TX queue, seen as part of the same net core queue */
/* XXX is this a thing on EF100? */
static inline struct efx_tx_queue *efx_tx_queue_partner(struct efx_tx_queue *tx_queue)
@ -97,20 +85,6 @@ static inline struct efx_tx_queue *efx_tx_queue_partner(struct efx_tx_queue *tx_
return tx_queue + EFX_TXQ_TYPE_OFFLOAD;
}
/* 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. This also ensures that only one packet at a time can be
* using the PIO buffer.
*/
static inline bool efx_nic_may_tx_pio(struct efx_tx_queue *tx_queue)
{
struct efx_tx_queue *partner = efx_tx_queue_partner(tx_queue);
return tx_queue->piobuf && efx_nic_tx_is_empty(tx_queue) &&
efx_nic_tx_is_empty(partner);
}
int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
bool *data_mapped);
@ -125,7 +99,7 @@ int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
static inline bool efx_nic_may_push_tx_desc(struct efx_tx_queue *tx_queue,
unsigned int write_count)
{
bool was_empty = __efx_nic_tx_is_empty(tx_queue, write_count);
bool was_empty = efx_nic_tx_is_empty(tx_queue, write_count);
tx_queue->empty_read_count = 0;
return was_empty && tx_queue->write_count - write_count == 1;

26
drivers/net/ethernet/sfc/tx.c
View File

@ -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;