Re: [PATCHv2 1/1] IB/rxe: remove unnecessary skb_clone

[Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Tue, Feb 13, 2018 at 02:59:46AM -0500, Zhu Yanjun wrote:
> In send_atomic_ack function, it is not necessary make a

s/make/to make

> skb_clone. To gain better performance(high throughput and

s/e(h/e (h

> low latency), this skb_clone is removed.
> 
> The following tests are made.
> 
>  server                       client
> ---------                    ---------
> |1.1.1.1|<----rxe-channel--->|1.1.1.2|
> ---------                    ---------
> 
> On server: rping -s -a 1.1.1.1 -v -C 1000 -S 512
> On client: rping -c -a 1.1.1.1 -v -C 1000 -S 512
> 
> The kernel config CONFIG_DEBUG_KMEMLEAK is enabled on both server
> and client.
> 
> This test runs for several hours. There is no memory leak and the whole
> system can work well.
> 
> As the above network, the following tests are made.
> 
> Server: ibv_rc_pingpong -d rxe0 -g 1
> Client: ibv_rc_pingpong -d rxe0 -g 1 1.1.1.1
> 
> The result on Server(10 tests are made).
> Before:
> Throughput is 137.07 Mbit/sec
> Latency is 517.76 usec/iter
> 
> After:
> Throughput is 148.85 Mbit/sec
> Latency is 476.64 usec/iter
> 
> The throughput is enhanced and the latency is reduced.
> 
> CC: Srinivas Eeda <srinivas.eeda-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> CC: Junxiao Bi <junxiao.bi-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Zhu Yanjun <yanjun.zhu-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> ---
> V1-->V2: 10 tests are made. From throughput and latency, the performance is better.
> ---
>  drivers/infiniband/sw/rxe/rxe_resp.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
> index d37bb9b..6d01d16 100644
> --- a/drivers/infiniband/sw/rxe/rxe_resp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
> @@ -969,7 +969,6 @@ static int send_atomic_ack(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
>  	int rc = 0;
>  	struct rxe_pkt_info ack_pkt;
>  	struct sk_buff *skb;
> -	struct sk_buff *skb_copy;
>  	struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
>  	struct resp_res *res;
>  
> @@ -981,15 +980,6 @@ static int send_atomic_ack(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
>  		goto out;
>  	}
>  
> -	skb_copy = skb_clone(skb, GFP_ATOMIC);
> -	if (skb_copy)
> -		rxe_add_ref(qp); /* for the new SKB */

Are you sure we don't need this?

> -	else {
> -		pr_warn("Could not clone atomic response\n");
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> -
>  	res = &qp->resp.resources[qp->resp.res_head];
>  	free_rd_atomic_resource(qp, res);
>  	rxe_advance_resp_resource(qp);
> @@ -998,17 +988,16 @@ static int send_atomic_ack(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
>  	memset((unsigned char *)SKB_TO_PKT(skb) + sizeof(ack_pkt), 0,
>  	       sizeof(skb->cb) - sizeof(ack_pkt));
>  
> +	refcount_inc(&skb->users);
>  	res->type = RXE_ATOMIC_MASK;
>  	res->atomic.skb = skb;
>  	res->first_psn = ack_pkt.psn;
>  	res->last_psn  = ack_pkt.psn;
>  	res->cur_psn   = ack_pkt.psn;
>  
> -	rc = rxe_xmit_packet(rxe, qp, &ack_pkt, skb_copy);
> +	rc = rxe_xmit_packet(rxe, qp, &ack_pkt, skb);
>  	if (rc) {
>  		pr_err_ratelimited("Failed sending ack\n");
> -		rxe_drop_ref(qp);
> -		kfree_skb(skb_copy);
>  	}

With this modification suggesting to remove the curly braces.

>  
>  out:
> -- 
> 2.7.4
> 
> --
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