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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>
This commit is contained in:
David Riddoch 2012-04-11 13:12:41 +01:00 committed by Ben Hutchings
parent da9ca50582
commit 64235187c2
1 changed files with 12 additions and 6 deletions
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18
drivers/net/ethernet/sfc/rx.c
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@ -76,7 +76,7 @@ static int rx_alloc_method = RX_ALLOC_METHOD_AUTO;
/* 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 @@ void efx_fast_push_rx_descriptors(struct efx_rx_queue *rx_queue)
}
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 @@ int efx_probe_rx_queue(struct efx_rx_queue *rx_queue)
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 @@ void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
/* 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_PARM_DESC(rx_alloc_method, "Allocation method used for RX buffers");
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 (%)");