netdev - Re: [PATCH v2 bpf-next] net: veth: alloc skb in bulk for ndo_xdp

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Message-ID: <20210129214114.GA20729@lore-desk>
Date:   Fri, 29 Jan 2021 22:41:14 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Toshiaki Makita <toshiaki.makita1@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        lorenzo.bianconi@...hat.com, brouer@...hat.com, toke@...hat.com
Subject: Re: [PATCH v2 bpf-next] net: veth: alloc skb in bulk for ndo_xdp_xmit

> On 2021/01/29 4:41, Lorenzo Bianconi wrote:
> > Split ndo_xdp_xmit and ndo_start_xmit use cases in veth_xdp_rcv routine
> > in order to alloc skbs in bulk for XDP_PASS verdict.
> > Introduce xdp_alloc_skb_bulk utility routine to alloc skb bulk list.
> > The proposed approach has been tested in the following scenario:
> > 
> > eth (ixgbe) --> XDP_REDIRECT --> veth0 --> (remote-ns) veth1 --> XDP_PASS
> > 
> > XDP_REDIRECT: xdp_redirect_map bpf sample
> > XDP_PASS: xdp_rxq_info bpf sample
> > 
> > traffic generator: pkt_gen sending udp traffic on a remote device
> > 
> > bpf-next master: ~3.64Mpps
> > bpf-next + skb bulking allocation: ~3.75Mpps
> > 
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> ...
> > +/* frames array contains VETH_XDP_BATCH at most */
> > +static void veth_xdp_rcv_batch(struct veth_rq *rq, void **frames,
> > +			       int n_xdpf, struct veth_xdp_tx_bq *bq,
> > +			       struct veth_stats *stats)
> > +{
> > +	void *skbs[VETH_XDP_BATCH];
> > +	int i, n_skb = 0;
> > +
> > +	for (i = 0; i < n_xdpf; i++) {
> > +		struct xdp_frame *frame = frames[i];
> > +
> > +		stats->xdp_bytes += frame->len;
> > +		frame = veth_xdp_rcv_one(rq, frame, bq, stats);
> > +		if (frame)
> > +			frames[n_skb++] = frame;
> > +	}
> 
> Maybe we can move this block to veth_xdp_rcv() and make the logic even more simple?
> 
> Something like this:
> 
> static int veth_xdp_rcv(struct veth_rq *rq, int budget,
> 	...
> 		if (veth_is_xdp_frame(ptr)) {
> 			struct xdp_frame *frame = veth_ptr_to_xdp(ptr);
> 
> 			stats->xdp_bytes += frame->len;
> 			frame = veth_xdp_rcv_one(rq, frame, bq, stats);
> 			if (frame) {
> 				xdpf[n_xdpf++] = frame;
> 				if (n_xdpf == VETH_XDP_BATCH) {
> 					veth_xdp_rcv_batch(rq, xdpf, n_xdpf, bq,
> 							   stats);
> 					n_xdpf = 0;
> 				}
> 			}
> 
> Then we can fully make use of skb bulk allocation as xdpf[] does not include
> frames which may be XDP_TX'ed or XDP_REDIRECT'ed.
> 
> WDYT?

I gues the code is more readable, I will fix in v3. Thanks.

Regards,
Lorenzo

> 
> Toshiaki Makita

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