i40e/i40evf: adjust interrupt throttle less frequently
The adaptive ITR (interrupt throttle rate) algorithm was adjusting
the hardware's interrupt rate too frequently. This caused a lot
of variation in the interrupt rate for fairly constant workloads.
Change the code to have a counter and adjust only once every N
number of interrupts.
Change-ID: I0460f1f86571037484eca5aca36ac4d889cb8389
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@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/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index d76fe4a..47e9a90 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -348,10 +348,12 @@
* The math works out because the divisor is in 10^(-6) which
* turns the bytes/us input value into MB/s values, but
* make sure to use usecs, as the register values written
- * are in 2 usec increments in the ITR registers.
+ * are in 2 usec increments in the ITR registers, and make sure
+ * to use the smoothed values that the countdown timer gives us.
*/
- usecs = (rc->itr << 1);
+ usecs = (rc->itr << 1) * ITR_COUNTDOWN_START;
bytes_per_int = rc->total_bytes / usecs;
+
switch (new_latency_range) {
case I40E_LOWEST_LATENCY:
if (bytes_per_int > 10)
@@ -1245,8 +1247,18 @@
int vector;
vector = (q_vector->v_idx + vsi->base_vector);
+
+ /* avoid dynamic calculation if in countdown mode OR if
+ * all dynamic is disabled
+ */
rxval = txval = i40e_buildreg_itr(I40E_ITR_NONE, 0);
+ if (q_vector->itr_countdown > 0 ||
+ (!ITR_IS_DYNAMIC(vsi->rx_itr_setting) &&
+ !ITR_IS_DYNAMIC(vsi->tx_itr_setting))) {
+ goto enable_int;
+ }
+
if (ITR_IS_DYNAMIC(vsi->rx_itr_setting)) {
rx = i40e_set_new_dynamic_itr(&q_vector->rx);
rxval = i40e_buildreg_itr(I40E_RX_ITR, q_vector->rx.itr);
@@ -1282,8 +1294,15 @@
wr32(hw, INTREG(vector - 1), rxval);
}
+enable_int:
if (!test_bit(__I40E_DOWN, &vsi->state))
wr32(hw, INTREG(vector - 1), txval);
+
+ if (q_vector->itr_countdown)
+ q_vector->itr_countdown--;
+ else
+ q_vector->itr_countdown = ITR_COUNTDOWN_START;
+
}
/**