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sfc: use tx_queue->old_read_count in EF100 TX path

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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>
This commit is contained in:
Edward Cree 2020-09-03 22:34:57 +01:00 committed by Jakub Kicinski
parent 8cb2675634
commit 5374d6024c
2 changed files with 20 additions and 2 deletions
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8
drivers/net/ethernet/sfc/ef100_tx.c
View File

@ -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);
}

14
drivers/net/ethernet/sfc/net_driver.h
View File

@ -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