net: piggy back on the memory barrier in bql when waking queues

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Drivers call netdev_tx_completed_queue() right before
netif_txq_maybe_wake(). If BQL is enabled netdev_tx_completed_queue()
should issue a memory barrier, so we can depend on that separating
the stop check from the consumer index update, instead of adding
another barrier in netif_txq_maybe_wake().

This matters more than the barriers on the xmit path, because
the wake condition is almost always true. So we issue the
consumer side barrier often.

Wrap netdev_tx_completed_queue() in a local helper to issue
the barrier even if BQL is disabled. Keep the same semantics
as netdev_tx_completed_queue() (barrier only if bytes != 0)
to make it clear that the barrier is conditional.

Plus since macro gets pkt/byte counts as arguments now -
we can skip waking if there were no packets completed.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Jakub Kicinski 2023-04-06 18:25:36 -07:00

parent 08a096780d

commit 301f227fc8

4 changed files with 38 additions and 21 deletions

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6

drivers/net/ethernet/broadcom/bnxt/bnxt.c

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12

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

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2

include/linux/netdevice.h

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39

include/net/netdev_queues.h

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