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sfc: add support for skb->xmit_more

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Don't ring the doorbell, and don't do PIO.  This will also prevent
 TX Push, because there will be more than one buffer waiting when
 the doorbell is rung.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Edward Cree
2014-10-17 15:32:25 +01:00
committed by David S. Miller
parent 6cc69f2a40
commit 70b33fb0dd
2 changed files with 43 additions and 29 deletions
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29
drivers/net/ethernet/sfc/nic.h
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@@ -71,9 +71,17 @@ efx_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index)
return ((efx_qword_t *) (tx_queue->txd.buf.addr)) + index;
}
/* Report whether the NIC considers this TX queue empty, given the
* write_count used for the last doorbell push. May return false
* negative.
/* Get partner of a TX queue, seen as part of the same net core queue */
static struct efx_tx_queue *efx_tx_queue_partner(struct efx_tx_queue *tx_queue)
{
if (tx_queue->queue & EFX_TXQ_TYPE_OFFLOAD)
return tx_queue - EFX_TXQ_TYPE_OFFLOAD;
else
return tx_queue + EFX_TXQ_TYPE_OFFLOAD;
}
/* 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)
@@ -86,9 +94,18 @@ 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;
}
static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue)
/* 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)
{
return __efx_nic_tx_is_empty(tx_queue, tx_queue->write_count);
struct efx_tx_queue *partner = efx_tx_queue_partner(tx_queue);
return tx_queue->piobuf &&
__efx_nic_tx_is_empty(tx_queue, tx_queue->insert_count) &&
__efx_nic_tx_is_empty(partner, partner->insert_count);
}
/* Decide whether to push a TX descriptor to the NIC vs merely writing
@@ -96,6 +113,8 @@ static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue)
* descriptor to an empty queue, but is otherwise pointless. Further,
* Falcon and Siena have hardware bugs (SF bug 33851) that may be
* triggered if we don't check this.
* We use the write_count used for the last doorbell push, to get the
* NIC's view of the tx queue.
*/
static inline bool efx_nic_may_push_tx_desc(struct efx_tx_queue *tx_queue,
unsigned int write_count)