RE: [PATCH] net: mana: Batch ringing RX queue doorbell on receiving packets

[Haiyang Zhang]

> -----Original Message-----
> From: longli@xxxxxxxxxxxxxxxxx <longli@xxxxxxxxxxxxxxxxx>
> Sent: Thursday, June 15, 2023 7:28 PM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Wei Liu <wei.liu@xxxxxxxxxx>; Dexuan Cui
> <decui@xxxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric
> Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>; Leon Romanovsky <leon@xxxxxxxxxx>; Shradha
> Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx>; Ajay Sharma
> <sharmaajay@xxxxxxxxxxxxx>; Shachar Raindel <shacharr@xxxxxxxxxxxxx>;
> Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>; linux-
> hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Cc: linux-rdma@xxxxxxxxxxxxxxx; Long Li <longli@xxxxxxxxxxxxx>;
> stable@xxxxxxxxxxxxxxx
> Subject: [PATCH] net: mana: Batch ringing RX queue doorbell on receiving
> packets
> 
> From: Long Li <longli@xxxxxxxxxxxxx>
> 
> It's inefficient to ring the doorbell page every time a WQE is posted to
> the received queue.
> 
> Move the code for ringing doorbell page to where after we have posted all
> WQEs to the receive queue during a callback from napi_poll().
> 
> Tests showed no regression in network latency benchmarks.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network
> Adapter (MANA)")
> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c
> b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index cd4d5ceb9f2d..ef1f0ce8e44d 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -1383,8 +1383,8 @@ static void mana_post_pkt_rxq(struct mana_rxq
> *rxq)
> 
>  	recv_buf_oob = &rxq->rx_oobs[curr_index];
> 
> -	err = mana_gd_post_and_ring(rxq->gdma_rq, &recv_buf_oob-
> >wqe_req,
> -				    &recv_buf_oob->wqe_inf);
> +	err = mana_gd_post_work_request(rxq->gdma_rq, &recv_buf_oob-
> >wqe_req,
> +					&recv_buf_oob->wqe_inf);
>  	if (WARN_ON_ONCE(err))
>  		return;
> 
> @@ -1654,6 +1654,12 @@ static void mana_poll_rx_cq(struct mana_cq *cq)
>  		mana_process_rx_cqe(rxq, cq, &comp[i]);
>  	}
> 
> +	if (comp_read) {
> +		struct gdma_context *gc = rxq->gdma_rq->gdma_dev-
> >gdma_context;
> +
> +		mana_gd_wq_ring_doorbell(gc, rxq->gdma_rq);
> +	}
> +

Thank you!

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>