cxgb4: Add low latency socket busy_poll support
cxgb_busy_poll, corresponding to ndo_busy_poll, gets called by the socket
waiting for data.
With busy_poll enabled, improvement is seen in latency numbers as observed by
collecting netperf TCP_RR numbers.
Below are latency number, with and without busy-poll, in a switched environment
for a particular msg size:
netperf command: netperf -4 -H <ip> -l 30 -t TCP_RR -- -r1,1
Latency without busy-poll: ~16.25 us
Latency with busy-poll : ~08.79 us
Based on original work by Kumar Sanghvi <kumaras@chelsio.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/chelsio/cxgb4/t4_values.h b/drivers/net/ethernet/chelsio/cxgb4/t4_values.h
index a404844..997ec87 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/t4_values.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/t4_values.h
@@ -59,6 +59,7 @@
/* GTS register */
#define SGE_TIMERREGS 6
+#define TIMERREG_COUNTER0_X 0
/* T5 and later support a new BAR2-based doorbell mechanism for Egress Queues.
* The User Doorbells are each 128 bytes in length with a Simple Doorbell at