sfc: Remove TX completions from adaptive IRQ scoring

RX and TX completions on the same event queue are generally not associated
with the same flows.  The inclusion of TX completions in the adaptive IRQ
score is more of a source of noise rather than useful feedback.  Therefore,
do not include them in the score, and adjust the default threshold scores
down.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/efx.c

@@ -163,12 +163,12 @@ static int phy_flash_cfg;
 module_param(phy_flash_cfg, int, 0644);
 MODULE_PARM_DESC(phy_flash_cfg, "Set PHYs into reflash mode initially");
 
-static unsigned irq_adapt_low_thresh = 10000;
+static unsigned irq_adapt_low_thresh = 8000;
 module_param(irq_adapt_low_thresh, uint, 0644);
 MODULE_PARM_DESC(irq_adapt_low_thresh,
 		 "Threshold score for reducing IRQ moderation");
 
-static unsigned irq_adapt_high_thresh = 20000;
+static unsigned irq_adapt_high_thresh = 16000;
 module_param(irq_adapt_high_thresh, uint, 0644);
 MODULE_PARM_DESC(irq_adapt_high_thresh,
 		 "Threshold score for increasing IRQ moderation");

drivers/net/ethernet/sfc/nic.c

@@ -822,7 +822,6 @@ efx_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
 			channel, tx_ev_q_label % EFX_TXQ_TYPES);
 		tx_packets = ((tx_ev_desc_ptr - tx_queue->read_count) &
 			      tx_queue->ptr_mask);
-		channel->irq_mod_score += tx_packets;
 		efx_xmit_done(tx_queue, tx_ev_desc_ptr);
 	} else if (EFX_QWORD_FIELD(*event, FSF_AZ_TX_EV_WQ_FF_FULL)) {
 		/* Rewrite the FIFO write pointer */