From 0574bb806dad29a3dada0ee42b01645477d48282 Mon Sep 17 00:00:00 2001 From: Arthur Kiyanovski Date: Thu, 11 Oct 2018 11:26:23 +0300 Subject: [PATCH] net: ena: limit refill Rx threshold to 256 to avoid latency issues Currently Rx refill is done when the number of required descriptors is above 1/8 queue size. With a default of 1024 entries per queue the threshold is 128 descriptors. There is intention to increase the queue size to 8196 entries. In this case threshold of 1024 descriptors is too large and can hurt latency. Add another limitation to Rx threshold to be at most 256 descriptors. Signed-off-by: Arthur Kiyanovski Signed-off-by: David S. Miller --- drivers/net/ethernet/amazon/ena/ena_netdev.c | 4 +++- drivers/net/ethernet/amazon/ena/ena_netdev.h | 5 +++-- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c index 9927a5b76d7d..e71bf82ba753 100644 --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c @@ -1122,7 +1122,9 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi, rx_ring->next_to_clean = next_to_clean; refill_required = ena_com_free_desc(rx_ring->ena_com_io_sq); - refill_threshold = rx_ring->ring_size / ENA_RX_REFILL_THRESH_DIVIDER; + refill_threshold = + min_t(int, rx_ring->ring_size / ENA_RX_REFILL_THRESH_DIVIDER, + ENA_RX_REFILL_THRESH_PACKET); /* Optimization, try to batch new rx buffers */ if (refill_required > refill_threshold) { diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.h b/drivers/net/ethernet/amazon/ena/ena_netdev.h index a16baf0124d5..0cf35ae77884 100644 --- a/drivers/net/ethernet/amazon/ena/ena_netdev.h +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.h @@ -106,10 +106,11 @@ */ #define ENA_TX_POLL_BUDGET_DIVIDER 4 -/* Refill Rx queue when number of available descriptors is below - * QUEUE_SIZE / ENA_RX_REFILL_THRESH_DIVIDER +/* Refill Rx queue when number of required descriptors is above + * QUEUE_SIZE / ENA_RX_REFILL_THRESH_DIVIDER or ENA_RX_REFILL_THRESH_PACKET */ #define ENA_RX_REFILL_THRESH_DIVIDER 8 +#define ENA_RX_REFILL_THRESH_PACKET 256 /* Number of queues to check for missing queues per timer service */ #define ENA_MONITORED_TX_QUEUES 4 -- 2.30.2