For controllers that have TX interrupt moderation capability,

request TX completion interrupt for every 8-th frames. Previously
dc(4) requested TX completion interrupt if number of queued TX
descriptors is greater than 64. This caused a lot of TX completion
interrupt under high TX load once driver queued more than 64 TX
descriptors. It's quite normal to see more than 64 queued TX
descriptors under high TX load.
This change reduces the number of TX completion interrupts to be
less than 17k under high TX load. Because this change does not
generate TX completion interrupt for each frame, add reclaiming
transmitted buffers in dc_tick not to generate false watchdog
timeouts.
While I'm here add check for queued descriptors in dc_txeof() since
there is no more work to do when there is no pending descriptors.

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/dev/dc/if_dcreg.h b/sys/dev/dc/if_dcreg.h
index 066ea88..81c1b31 100644
--- a/sys/dev/dc/if_dcreg.h
+++ b/sys/dev/dc/if_dcreg.h
@@ -495,6 +495,7 @@ struct dc_chain_data {
 	bus_dmamap_t		dc_tx_map[DC_TX_LIST_CNT];
 	u_int32_t		*dc_sbuf;
 	u_int8_t		dc_pad[DC_MIN_FRAMELEN];
+	int			dc_tx_pkts;
 	int			dc_tx_first;
 	int			dc_tx_prod;
 	int			dc_tx_cons;