[PATCH] net/i40e: increase descriptor queue length to 8160

[Igor Gutorov]

According to the Intel X710/XXV710/XL710 Datasheet, the maximum receive
queue descriptor length is 0x1FE0 (8160 in base 10). This is specified
as QLEN in table 8-12, page 1083.

I've tested this change with an XXV710 NIC and it has positive effect on
performance under high load scenarios. Where previously I'd get
~2000 packets/sec miss rate, now I get only ~40 packets/sec miss rate.

Signed-off-by: Igor Gutorov <igootorov at gmail.com>
---
 drivers/net/i40e/i40e_rxtx.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/i40e/i40e_rxtx.h b/drivers/net/i40e/i40e_rxtx.h
index 2f2f890855..33fc9770d9 100644
--- a/drivers/net/i40e/i40e_rxtx.h
+++ b/drivers/net/i40e/i40e_rxtx.h
@@ -25,7 +25,7 @@
 #define I40E_RX_MAX_DATA_BUF_SIZE	(16 * 1024 - 128)
 
 #define	I40E_MIN_RING_DESC	64
-#define	I40E_MAX_RING_DESC	4096
+#define	I40E_MAX_RING_DESC	8160
 
 #define I40E_FDIR_NUM_TX_DESC   (I40E_FDIR_PRG_PKT_CNT << 1)
 #define I40E_FDIR_NUM_RX_DESC   (I40E_FDIR_PRG_PKT_CNT << 1)
-- 
2.45.1