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i40e/i40evf: bundle more descriptors when allocating buffers

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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>
This commit is contained in:
Jacob Keller 2017-09-07 08:05:52 -04:00 committed by Jeff Kirsher
parent 11f29003d6
commit 95bc2fb4c6
2 changed files with 2 additions and 2 deletions
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2
drivers/net/ethernet/intel/i40e/i40e_txrx.h
View File

@ -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)++; \

2
drivers/net/ethernet/intel/i40evf/i40e_txrx.h
View File

@ -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)++; \