[PATCH net-next 11/15] e1000e: Use __napi_schedule_irqoff()

[Tony Nguyen <anthony.l.nguyen@intel.com>]

From: Matt Vollrath <tactii@gmail.com>

The __napi_schedule_irqoff() macro is intended to bypass saving and
restoring IRQ state when scheduling is requested from an IRQ handler,
where hard interrupts are already disabled. Use this macro in all three
interrupt handlers.

This was tested on a system with an I218-V and MSI interrupts. Because
this is an optimization, I was interested in measuring the impact, so I
added ktime_get() time measurement to e1000_intr_msi and a print of the
last sample in the watchdog task. For each test case I ran a
bi-directional iperf3 to saturate the line. With some help from awk,
here are the statistics.

49 samples each, all units ns
previous: min 678 max 1265 mean 879.429 median 806 stddev 137.188
noirq:    min 707 max 1165 mean 811.857 median 790 stddev  89.486

According to this informal comparison, the mean time to handle an
interrupt from start to finish is improved by about 8% under load.

Signed-off-by: Matt Vollrath <tactii@gmail.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Michal Cohen <michalx.cohen@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 3bdeb5f0dbea..808e5cddd6a9 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -1803,7 +1803,7 @@ static irqreturn_t e1000_intr_msi(int __always_unused irq, void *data)
 		adapter->total_tx_packets = 0;
 		adapter->total_rx_bytes = 0;
 		adapter->total_rx_packets = 0;
-		__napi_schedule(&adapter->napi);
+		__napi_schedule_irqoff(&adapter->napi);
 	}
 
 	return IRQ_HANDLED;
@@ -1882,7 +1882,7 @@ static irqreturn_t e1000_intr(int __always_unused irq, void *data)
 		adapter->total_tx_packets = 0;
 		adapter->total_rx_bytes = 0;
 		adapter->total_rx_packets = 0;
-		__napi_schedule(&adapter->napi);
+		__napi_schedule_irqoff(&adapter->napi);
 	}
 
 	return IRQ_HANDLED;
@@ -1951,7 +1951,7 @@ static irqreturn_t e1000_intr_msix_rx(int __always_unused irq, void *data)
 	if (napi_schedule_prep(&adapter->napi)) {
 		adapter->total_rx_bytes = 0;
 		adapter->total_rx_packets = 0;
-		__napi_schedule(&adapter->napi);
+		__napi_schedule_irqoff(&adapter->napi);
 	}
 	return IRQ_HANDLED;
 }
-- 
2.47.1