Commit 73017f4e authored May 25, 2018 by Venkatesh Srinivas Committed by Jeff Kirsher Jul 26, 2018

igb: Use dma_wmb() instead of wmb() before doorbell writes



igb writes to doorbells to post transmit and receive descriptors;
after writing descriptors to memory but before writing to doorbells,
use dma_wmb() rather than wmb(). wmb() is more heavyweight than
necessary before doorbell writes.

On x86, this avoids SFENCEs before doorbell writes in both the
tx and rx refill paths.

Signed-off-by: Venkatesh Srinivas <venkateshs@google.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

parent 2a83fba6

drivers/net/ethernet/intel/igb/igb_main.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -6031,7 +6031,7 @@ static int igb_tx_map(struct igb_ring *tx_ring,
		* We also need this memory barrier to make certain all of the
		* status bits have been updated before next_to_watch is written.
		*/
		wmb();
		dma_wmb();

		/* set next_to_watch value indicating a packet is present */
		first->next_to_watch = tx_desc;
		@@ -8531,7 +8531,7 @@ void igb_alloc_rx_buffers(struct igb_ring *rx_ring, u16 cleaned_count)
		* applicable for weak-ordered memory model archs,
		* such as IA-64).
		*/
		wmb();
		dma_wmb();
		writel(i, rx_ring->tail);
		}
		}