| From 5840412e0c2a1bc96818038f1440f90ac8d796f4 Mon Sep 17 00:00:00 2001 |
| From: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com> |
| Date: Thu, 19 Mar 2020 23:08:09 +0530 |
| Subject: [PATCH] cxgb4: fix throughput drop during Tx backpressure |
| |
| commit 7affd80802afb6ca92dba47d768632fbde365241 upstream. |
| |
| commit 7c3bebc3d868 ("cxgb4: request the TX CIDX updates to status page") |
| reverted back to getting Tx CIDX updates via DMA, instead of interrupts, |
| introduced by commit d429005fdf2c ("cxgb4/cxgb4vf: Add support for SGE |
| doorbell queue timer") |
| |
| However, it missed reverting back several code changes where Tx CIDX |
| updates are not explicitly requested during backpressure when using |
| interrupt mode. These missed changes cause slow recovery during |
| backpressure because the corresponding interrupt no longer comes and |
| hence results in Tx throughput drop. |
| |
| So, revert back these missed code changes, as well, which will allow |
| explicitly requesting Tx CIDX updates when backpressure happens. |
| This enables the corresponding interrupt with Tx CIDX update message |
| to get generated and hence speed up recovery and restore back |
| throughput. |
| |
| Fixes: 7c3bebc3d868 ("cxgb4: request the TX CIDX updates to status page") |
| Fixes: d429005fdf2c ("cxgb4/cxgb4vf: Add support for SGE doorbell queue timer") |
| Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c |
| index 928bfea5457b..3af6d8376a66 100644 |
| --- a/drivers/net/ethernet/chelsio/cxgb4/sge.c |
| +++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c |
| @@ -1469,16 +1469,7 @@ out_free: dev_kfree_skb_any(skb); |
| * has opened up. |
| */ |
| eth_txq_stop(q); |
| - |
| - /* If we're using the SGE Doorbell Queue Timer facility, we |
| - * don't need to ask the Firmware to send us Egress Queue CIDX |
| - * Updates: the Hardware will do this automatically. And |
| - * since we send the Ingress Queue CIDX Updates to the |
| - * corresponding Ethernet Response Queue, we'll get them very |
| - * quickly. |
| - */ |
| - if (!q->dbqt) |
| - wr_mid |= FW_WR_EQUEQ_F | FW_WR_EQUIQ_F; |
| + wr_mid |= FW_WR_EQUEQ_F | FW_WR_EQUIQ_F; |
| } |
| |
| wr = (void *)&q->q.desc[q->q.pidx]; |
| @@ -1792,16 +1783,7 @@ static netdev_tx_t cxgb4_vf_eth_xmit(struct sk_buff *skb, |
| * has opened up. |
| */ |
| eth_txq_stop(txq); |
| - |
| - /* If we're using the SGE Doorbell Queue Timer facility, we |
| - * don't need to ask the Firmware to send us Egress Queue CIDX |
| - * Updates: the Hardware will do this automatically. And |
| - * since we send the Ingress Queue CIDX Updates to the |
| - * corresponding Ethernet Response Queue, we'll get them very |
| - * quickly. |
| - */ |
| - if (!txq->dbqt) |
| - wr_mid |= FW_WR_EQUEQ_F | FW_WR_EQUIQ_F; |
| + wr_mid |= FW_WR_EQUEQ_F | FW_WR_EQUIQ_F; |
| } |
| |
| /* Start filling in our Work Request. Note that we do _not_ handle |
| @@ -2924,26 +2906,6 @@ static void t4_tx_completion_handler(struct sge_rspq *rspq, |
| } |
| |
| txq = &s->ethtxq[pi->first_qset + rspq->idx]; |
| - |
| - /* We've got the Hardware Consumer Index Update in the Egress Update |
| - * message. If we're using the SGE Doorbell Queue Timer mechanism, |
| - * these Egress Update messages will be our sole CIDX Updates we get |
| - * since we don't want to chew up PCIe bandwidth for both Ingress |
| - * Messages and Status Page writes. However, The code which manages |
| - * reclaiming successfully DMA'ed TX Work Requests uses the CIDX value |
| - * stored in the Status Page at the end of the TX Queue. It's easiest |
| - * to simply copy the CIDX Update value from the Egress Update message |
| - * to the Status Page. Also note that no Endian issues need to be |
| - * considered here since both are Big Endian and we're just copying |
| - * bytes consistently ... |
| - */ |
| - if (txq->dbqt) { |
| - struct cpl_sge_egr_update *egr; |
| - |
| - egr = (struct cpl_sge_egr_update *)rsp; |
| - WRITE_ONCE(txq->q.stat->cidx, egr->cidx); |
| - } |
| - |
| t4_sge_eth_txq_egress_update(adapter, txq, -1); |
| } |
| |
| -- |
| 2.7.4 |
| |
