[PATCH net] cxgb4: request the TX CIDX updates to status page

[PATCH net] cxgb4: request the TX CIDX updates to status page

[Raju Rangoju]

For adapters which support the SGE Doorbell Queue Timer facility,
we configured the Ethernet TX Queues to send CIDX Updates to the
Associated Ethernet RX Response Queue with CPL_SGE_EGR_UPDATE
messages to allow us to respond more quickly to the CIDX Updates.
But, this was adding load to PCIe Link RX bandwidth and,
potentially, resulting in higher CPU Interrupt load.

This patch requests the HW to deliver the CIDX updates to the TX
queue status page rather than generating an ingress queue message
(as an interrupt). With this patch, the load on RX bandwidth is
reduced and a substantial improvement in BW is noticed at lower
IO sizes.

Fixes: d429005fdf2c ("cxgb4/cxgb4vf: Add support for SGE doorbell queue timer")
Signed-off-by: Raju Rangoju <rajur@chelsio.com>
---
 drivers/net/ethernet/chelsio/cxgb4/sge.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index b3da81e90132..928bfea5457b 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -3791,15 +3791,11 @@ int t4_sge_alloc_eth_txq(struct adapter *adap, struct sge_eth_txq *txq,
 	 * write the CIDX Updates into the Status Page at the end of the
 	 * TX Queue.
 	 */
-	c.autoequiqe_to_viid = htonl((dbqt
-				      ? FW_EQ_ETH_CMD_AUTOEQUIQE_F
-				      : FW_EQ_ETH_CMD_AUTOEQUEQE_F) |
+	c.autoequiqe_to_viid = htonl(FW_EQ_ETH_CMD_AUTOEQUEQE_F |
 				     FW_EQ_ETH_CMD_VIID_V(pi->viid));
 
 	c.fetchszm_to_iqid =
-		htonl(FW_EQ_ETH_CMD_HOSTFCMODE_V(dbqt
-						 ? HOSTFCMODE_INGRESS_QUEUE_X
-						 : HOSTFCMODE_STATUS_PAGE_X) |
+		htonl(FW_EQ_ETH_CMD_HOSTFCMODE_V(HOSTFCMODE_STATUS_PAGE_X) |
 		      FW_EQ_ETH_CMD_PCIECHN_V(pi->tx_chan) |
 		      FW_EQ_ETH_CMD_FETCHRO_F | FW_EQ_ETH_CMD_IQID_V(iqid));
 
-- 
2.9.5

Re: [PATCH net] cxgb4: request the TX CIDX updates to status page

[David Miller]

From: Raju Rangoju <rajur@chelsio.com>
Date: Wed, 23 Oct 2019 23:03:55 +0530

> For adapters which support the SGE Doorbell Queue Timer facility,
> we configured the Ethernet TX Queues to send CIDX Updates to the
> Associated Ethernet RX Response Queue with CPL_SGE_EGR_UPDATE
> messages to allow us to respond more quickly to the CIDX Updates.
> But, this was adding load to PCIe Link RX bandwidth and,
> potentially, resulting in higher CPU Interrupt load.
> 
> This patch requests the HW to deliver the CIDX updates to the TX
> queue status page rather than generating an ingress queue message
> (as an interrupt). With this patch, the load on RX bandwidth is
> reduced and a substantial improvement in BW is noticed at lower
> IO sizes.
> 
> Fixes: d429005fdf2c ("cxgb4/cxgb4vf: Add support for SGE doorbell queue timer")
> Signed-off-by: Raju Rangoju <rajur@chelsio.com>

Applied and queued up for -stable.