i40e/i40evf: bundle more descriptors when allocating buffers

Double the number of descriptors we'll bundle into one tail bump when
receiving. Empirical testing has shown that we reduce CPU utilization
and don't appear to reduce throughput or packet rate. 32 seems to be the
sweet spot, as it's half the default polling budget, so we'd essentially
reduce from 4 tail writes when polling down to 2. Increasing this up to
64 appears to have negative impacts as it may become possible that we
don't bump the tail each time we get polled, which could cause a long
delay between returning descriptors to the hardware.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index c3156aa3f709f0bc3369f21d2ecfe3b0846ba436..ff57ae451524f2994b40155a834acd90f7685fb6 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -208,7 +208,7 @@ static inline bool i40e_test_staterr(union i40e_rx_desc *rx_desc,
 }
 
 /* How many Rx Buffers do we bundle into one write to the hardware ? */
-#define I40E_RX_BUFFER_WRITE   16      /* Must be power of 2 */
+#define I40E_RX_BUFFER_WRITE   32      /* Must be power of 2 */
 #define I40E_RX_INCREMENT(r, i) \
        do {                                    \
                (i)++;                          \

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
index 8f9830d7649a76f6dd8fe979d4d98bd3fd57d221..8d26c85d12e1311dfa3fc413a8d29505febd8c01 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.h
@@ -191,7 +191,7 @@ static inline bool i40e_test_staterr(union i40e_rx_desc *rx_desc,
 }
 
 /* How many Rx Buffers do we bundle into one write to the hardware ? */
-#define I40E_RX_BUFFER_WRITE   16      /* Must be power of 2 */
+#define I40E_RX_BUFFER_WRITE   32      /* Must be power of 2 */
 #define I40E_RX_INCREMENT(r, i) \
        do {                                    \
                (i)++;                          \