sfc: By default refill RX rings as soon as space for a batch
Previously we refilled with much larger batches, which caused large latency
spikes. We now have many more much much smaller spikes!
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/rx.c b/drivers/net/ethernet/sfc/rx.c
index 254fec8..243e91f 100644
--- a/drivers/net/ethernet/sfc/rx.c
+++ b/drivers/net/ethernet/sfc/rx.c
@@ -76,7 +76,7 @@
/* This is the percentage fill level below which new RX descriptors
* will be added to the RX descriptor ring.
*/
-static unsigned int rx_refill_threshold = 90;
+static unsigned int rx_refill_threshold;
/*
* RX maximum head room required.
@@ -363,8 +363,7 @@
}
space = rx_queue->max_fill - fill_level;
- if (space < EFX_RX_BATCH)
- goto out;
+ EFX_BUG_ON_PARANOID(space < EFX_RX_BATCH);
netif_vdbg(rx_queue->efx, rx_status, rx_queue->efx->net_dev,
"RX queue %d fast-filling descriptor ring from"
@@ -676,7 +675,7 @@
void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
{
struct efx_nic *efx = rx_queue->efx;
- unsigned int max_fill, trigger;
+ unsigned int max_fill, trigger, max_trigger;
netif_dbg(rx_queue->efx, drv, rx_queue->efx->net_dev,
"initialising RX queue %d\n", efx_rx_queue_index(rx_queue));
@@ -689,7 +688,14 @@
/* Initialise limit fields */
max_fill = efx->rxq_entries - EFX_RXD_HEAD_ROOM;
- trigger = max_fill * min(rx_refill_threshold, 100U) / 100U;
+ max_trigger = max_fill - EFX_RX_BATCH;
+ if (rx_refill_threshold != 0) {
+ trigger = max_fill * min(rx_refill_threshold, 100U) / 100U;
+ if (trigger > max_trigger)
+ trigger = max_trigger;
+ } else {
+ trigger = max_trigger;
+ }
rx_queue->max_fill = max_fill;
rx_queue->fast_fill_trigger = trigger;
@@ -739,5 +745,5 @@
module_param(rx_refill_threshold, uint, 0444);
MODULE_PARM_DESC(rx_refill_threshold,
- "RX descriptor ring fast/slow fill threshold (%)");
+ "RX descriptor ring refill threshold (%)");