diff mbox series

[PATCHv12,bpf-next,1/6] bpf: run devmap xdp_prog on flush instead of bulk enqueue

Message ID 20201216143036.2296568-2-liuhangbin@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series xdp: add a new helper for dev map multicast support | expand

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netdev/stable success Stable not CCed

Commit Message

Hangbin Liu Dec. 16, 2020, 2:30 p.m. UTC 
From: Jesper Dangaard Brouer <brouer@redhat.com>

This changes the devmap XDP program support to run the program when the
bulk queue is flushed instead of before the frame is enqueued. This has
a couple of benefits:

- It "sorts" the packets by destination devmap entry, and then runs the
  same BPF program on all the packets in sequence. This ensures that we
  keep the XDP program and destination device properties hot in I-cache.

- It makes the multicast implementation simpler because it can just
  enqueue packets using bq_enqueue() without having to deal with the
  devmap program at all.

The drawback is that if the devmap program drops the packet, the enqueue
step is redundant. However, arguably this is mostly visible in a
micro-benchmark, and with more mixed traffic the I-cache benefit should
win out. The performance impact of just this patch is as follows:

Using xdp_redirect_map(with a 2nd xdp_prog patch[1]) in sample/bpf and send
pkts via pktgen cmd:
./pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -t 10 -s 64

There are about +/- 0.1M deviation for native testing, the performance
improved for the base-case, but some drop back with xdp devmap prog attached.

Version          | Test                           | Generic | Native | Native + 2nd xdp_prog
5.10 rc6         | xdp_redirect_map   i40e->i40e  |    2.0M |   9.1M |  8.0M
5.10 rc6         | xdp_redirect_map   i40e->veth  |    1.7M |  11.0M |  9.7M
5.10 rc6 + patch | xdp_redirect_map   i40e->i40e  |    2.0M |   9.5M |  7.5M
5.10 rc6 + patch | xdp_redirect_map   i40e->veth  |    1.7M |  11.6M |  9.1M

[1] https://patchwork.ozlabs.org/project/netdev/patch/20201208120159.2278277-1-liuhangbin@gmail.com/

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Hangbin Liu <haliu@redhat.com>
---
 kernel/bpf/devmap.c | 116 ++++++++++++++++++++++++++++----------------
 1 file changed, 73 insertions(+), 43 deletions(-)

Comments

David Ahern Dec. 17, 2020, 4:07 p.m. UTC | #1 
On 12/16/20 7:30 AM, Hangbin Liu wrote:
> @@ -327,40 +328,92 @@ bool dev_map_can_have_prog(struct bpf_map *map)
>  	return false;
>  }
>  
> +static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
> +				struct xdp_frame **frames, int n,
> +				struct net_device *dev)
> +{
> +	struct xdp_txq_info txq = { .dev = dev };
> +	struct xdp_buff xdp;
> +	int i, nframes = 0;
> +
> +	for (i = 0; i < n; i++) {
> +		struct xdp_frame *xdpf = frames[i];
> +		u32 act;
> +		int err;
> +
> +		xdp_convert_frame_to_buff(xdpf, &xdp);
> +		xdp.txq = &txq;
> +
> +		act = bpf_prog_run_xdp(xdp_prog, &xdp);
> +		switch (act) {
> +		case XDP_PASS:
> +			err = xdp_update_frame_from_buff(&xdp, xdpf);
> +			if (unlikely(err < 0))
> +				xdp_return_frame_rx_napi(xdpf);
> +			else
> +				frames[nframes++] = xdpf;
> +			break;
> +		default:
> +			bpf_warn_invalid_xdp_action(act);
> +			fallthrough;
> +		case XDP_ABORTED:
> +			trace_xdp_exception(dev, xdp_prog, act);
> +			fallthrough;
> +		case XDP_DROP:
> +			xdp_return_frame_rx_napi(xdpf);
> +			break;
> +		}
> +	}
> +	return n - nframes; /* dropped frames count */

just return nframes here, since ...

> +}
> +
>  static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
>  {
>  	struct net_device *dev = bq->dev;
>  	int sent = 0, drops = 0, err = 0;
> +	unsigned int cnt = bq->count;
> +	unsigned int xdp_drop;
>  	int i;
>  
> -	if (unlikely(!bq->count))
> +	if (unlikely(!cnt))
>  		return;
>  
> -	for (i = 0; i < bq->count; i++) {
> +	for (i = 0; i < cnt; i++) {
>  		struct xdp_frame *xdpf = bq->q[i];
>  
>  		prefetch(xdpf);
>  	}
>  
> -	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
> +	if (unlikely(bq->xdp_prog)) {
> +		xdp_drop = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
> +		cnt -= xdp_drop;

... that is apparently what you really want.

> +		if (!cnt) {
> +			sent = 0;
> +			drops = xdp_drop;
> +			goto out;
> +		}
> +	}
> +
> +	sent = dev->netdev_ops->ndo_xdp_xmit(dev, cnt, bq->q, flags);
>  	if (sent < 0) {
>  		err = sent;
>  		sent = 0;
>  		goto error;
>  	}
> -	drops = bq->count - sent;
> +	drops = (cnt - sent) + xdp_drop;
>  out:
>  	bq->count = 0;
>  
>  	trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, drops, err);
>  	bq->dev_rx = NULL;
> +	bq->xdp_prog = NULL;
>  	__list_del_clearprev(&bq->flush_node);
>  	return;
>  error:
>  	/* If ndo_xdp_xmit fails with an errno, no frames have been
>  	 * xmit'ed and it's our responsibility to them free all.
>  	 */
> -	for (i = 0; i < bq->count; i++) {
> +	for (i = 0; i < cnt; i++) {
>  		struct xdp_frame *xdpf = bq->q[i];
>  
>  		xdp_return_frame_rx_napi(xdpf);
> @@ -408,7 +461,8 @@ struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
>   * Thus, safe percpu variable access.
>   */
>  static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
> -		       struct net_device *dev_rx)
> +		       struct net_device *dev_rx,
> +		       struct bpf_dtab_netdev *dst)
>  {
>  	struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
>  	struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq);
> @@ -423,6 +477,14 @@ static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
>  	if (!bq->dev_rx)
>  		bq->dev_rx = dev_rx;
>  
> +	/* Store (potential) xdp_prog that run before egress to dev as
> +	 * part of bulk_queue.  This will be same xdp_prog for all
> +	 * xdp_frame's in bulk_queue, because this per-CPU store must
> +	 * be flushed from net_device drivers NAPI func end.
> +	 */
> +	if (dst && dst->xdp_prog && !bq->xdp_prog)
> +		bq->xdp_prog = dst->xdp_prog;


if you pass in xdp_prog through __xdp_enqueue you can reduce that to just:

	if (!bq->xdp_prog)
		bq->xdp_prog = xdp_prog;


>  	bq->q[bq->count++] = xdpf;
>  
>  	if (!bq->flush_node.prev)
> @@ -430,7 +492,8 @@ static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
>  }
>  
>  static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
> -			       struct net_device *dev_rx)
> +				struct net_device *dev_rx,
> +				struct bpf_dtab_netdev *dst)
>  {
>  	struct xdp_frame *xdpf;
>  	int err;
> @@ -446,42 +509,14 @@ static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
>  	if (unlikely(!xdpf))
>  		return -EOVERFLOW;
>  
> -	bq_enqueue(dev, xdpf, dev_rx);
> +	bq_enqueue(dev, xdpf, dev_rx, dst);
>  	return 0;
>  }
>  
> -static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
> -					 struct xdp_buff *xdp,
> -					 struct bpf_prog *xdp_prog)
> -{
> -	struct xdp_txq_info txq = { .dev = dev };
> -	u32 act;
> -
> -	xdp_set_data_meta_invalid(xdp);
> -	xdp->txq = &txq;
> -
> -	act = bpf_prog_run_xdp(xdp_prog, xdp);
> -	switch (act) {
> -	case XDP_PASS:
> -		return xdp;
> -	case XDP_DROP:
> -		break;
> -	default:
> -		bpf_warn_invalid_xdp_action(act);
> -		fallthrough;
> -	case XDP_ABORTED:
> -		trace_xdp_exception(dev, xdp_prog, act);
> -		break;
> -	}
> -
> -	xdp_return_buff(xdp);
> -	return NULL;
> -}
> -
>  int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
>  		    struct net_device *dev_rx)
>  {
> -	return __xdp_enqueue(dev, xdp, dev_rx);
> +	return __xdp_enqueue(dev, xdp, dev_rx, NULL);
>  }
>  
>  int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
> @@ -489,12 +524,7 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
>  {
>  	struct net_device *dev = dst->dev;
>  
> -	if (dst->xdp_prog) {
> -		xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog);
> -		if (!xdp)
> -			return 0;
> -	}
> -	return __xdp_enqueue(dev, xdp, dev_rx);
> +	return __xdp_enqueue(dev, xdp, dev_rx, dst);
>  }
>  
>  int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
>
Hangbin Liu Dec. 18, 2020, 9:43 a.m. UTC | #2 
Hi David,

Thanks for the comment.

On Thu, Dec 17, 2020 at 09:07:03AM -0700, David Ahern wrote:
> > +	return n - nframes; /* dropped frames count */
> 
> just return nframes here, since ...
> 
> > +		xdp_drop = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
> > +		cnt -= xdp_drop;
> 
> ... that is apparently what you really want.

I will fix this

> > +	if (dst && dst->xdp_prog && !bq->xdp_prog)
> > +		bq->xdp_prog = dst->xdp_prog;
> 
> 
> if you pass in xdp_prog through __xdp_enqueue you can reduce that to just:
> 
> 	if (!bq->xdp_prog)
> 		bq->xdp_prog = xdp_prog;

And this in the next PATCH version.

Thanks
Hangbin
Hangbin Liu Dec. 21, 2020, 8:38 a.m. UTC | #3 
Hi David,

I just aware that,
On Thu, Dec 17, 2020 at 09:07:03AM -0700, David Ahern wrote:
> > +static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
> > +				struct xdp_frame **frames, int n,
> > +				struct net_device *dev)
> > +{
> > +	struct xdp_txq_info txq = { .dev = dev };
> > +	struct xdp_buff xdp;
> > +	int i, nframes = 0;
> > +
> > +	for (i = 0; i < n; i++) {
> > +		struct xdp_frame *xdpf = frames[i];
> > +		u32 act;
> > +		int err;
> > +
> > +		xdp_convert_frame_to_buff(xdpf, &xdp);
> > +		xdp.txq = &txq;
> > +
> > +		act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > +		switch (act) {
> > +		case XDP_PASS:
> > +			err = xdp_update_frame_from_buff(&xdp, xdpf);
> > +			if (unlikely(err < 0))
> > +				xdp_return_frame_rx_napi(xdpf);
> > +			else
> > +				frames[nframes++] = xdpf;
> > +			break;
> > +		default:
> > +			bpf_warn_invalid_xdp_action(act);
> > +			fallthrough;
> > +		case XDP_ABORTED:
> > +			trace_xdp_exception(dev, xdp_prog, act);
> > +			fallthrough;
> > +		case XDP_DROP:
> > +			xdp_return_frame_rx_napi(xdpf);
> > +			break;
> > +		}
> > +	}
> > +	return n - nframes; /* dropped frames count */
> 
> just return nframes here, since ...

If we return nframes here,
> 
> > +}
> > +
> >  static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
> >  {
> >  	struct net_device *dev = bq->dev;
> >  	int sent = 0, drops = 0, err = 0;
> > +	unsigned int cnt = bq->count;
> > +	unsigned int xdp_drop;
> >  	int i;
> >  
> > -	if (unlikely(!bq->count))
> > +	if (unlikely(!cnt))
> >  		return;
> >  
> > -	for (i = 0; i < bq->count; i++) {
> > +	for (i = 0; i < cnt; i++) {
> >  		struct xdp_frame *xdpf = bq->q[i];
> >  
> >  		prefetch(xdpf);
> >  	}
> >  
> > -	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
> > +	if (unlikely(bq->xdp_prog)) {
> > +		xdp_drop = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
> > +		cnt -= xdp_drop;
> 
> ... that is apparently what you really want.

then this will be 

		cnt = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
		xdp_drop = bq->count - cnt;

So there is no much difference whether we return passed frames or dropped
frames.
> 
> > +		if (!cnt) {
> > +			sent = 0;
> > +			drops = xdp_drop;
> > +			goto out;
> > +		}
> > +	}

Thanks
Hangbin
diff mbox series

Patch

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index f6e9c68afdd4..2a83232cf63a 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -57,6 +57,7 @@  struct xdp_dev_bulk_queue {
 	struct list_head flush_node;
 	struct net_device *dev;
 	struct net_device *dev_rx;
+	struct bpf_prog *xdp_prog;
 	unsigned int count;
 };
 
@@ -327,40 +328,92 @@  bool dev_map_can_have_prog(struct bpf_map *map)
 	return false;
 }
 
+static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
+				struct xdp_frame **frames, int n,
+				struct net_device *dev)
+{
+	struct xdp_txq_info txq = { .dev = dev };
+	struct xdp_buff xdp;
+	int i, nframes = 0;
+
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdpf = frames[i];
+		u32 act;
+		int err;
+
+		xdp_convert_frame_to_buff(xdpf, &xdp);
+		xdp.txq = &txq;
+
+		act = bpf_prog_run_xdp(xdp_prog, &xdp);
+		switch (act) {
+		case XDP_PASS:
+			err = xdp_update_frame_from_buff(&xdp, xdpf);
+			if (unlikely(err < 0))
+				xdp_return_frame_rx_napi(xdpf);
+			else
+				frames[nframes++] = xdpf;
+			break;
+		default:
+			bpf_warn_invalid_xdp_action(act);
+			fallthrough;
+		case XDP_ABORTED:
+			trace_xdp_exception(dev, xdp_prog, act);
+			fallthrough;
+		case XDP_DROP:
+			xdp_return_frame_rx_napi(xdpf);
+			break;
+		}
+	}
+	return n - nframes; /* dropped frames count */
+}
+
 static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
 {
 	struct net_device *dev = bq->dev;
 	int sent = 0, drops = 0, err = 0;
+	unsigned int cnt = bq->count;
+	unsigned int xdp_drop;
 	int i;
 
-	if (unlikely(!bq->count))
+	if (unlikely(!cnt))
 		return;
 
-	for (i = 0; i < bq->count; i++) {
+	for (i = 0; i < cnt; i++) {
 		struct xdp_frame *xdpf = bq->q[i];
 
 		prefetch(xdpf);
 	}
 
-	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
+	if (unlikely(bq->xdp_prog)) {
+		xdp_drop = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
+		cnt -= xdp_drop;
+		if (!cnt) {
+			sent = 0;
+			drops = xdp_drop;
+			goto out;
+		}
+	}
+
+	sent = dev->netdev_ops->ndo_xdp_xmit(dev, cnt, bq->q, flags);
 	if (sent < 0) {
 		err = sent;
 		sent = 0;
 		goto error;
 	}
-	drops = bq->count - sent;
+	drops = (cnt - sent) + xdp_drop;
 out:
 	bq->count = 0;
 
 	trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, drops, err);
 	bq->dev_rx = NULL;
+	bq->xdp_prog = NULL;
 	__list_del_clearprev(&bq->flush_node);
 	return;
 error:
 	/* If ndo_xdp_xmit fails with an errno, no frames have been
 	 * xmit'ed and it's our responsibility to them free all.
 	 */
-	for (i = 0; i < bq->count; i++) {
+	for (i = 0; i < cnt; i++) {
 		struct xdp_frame *xdpf = bq->q[i];
 
 		xdp_return_frame_rx_napi(xdpf);
@@ -408,7 +461,8 @@  struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
  * Thus, safe percpu variable access.
  */
 static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
-		       struct net_device *dev_rx)
+		       struct net_device *dev_rx,
+		       struct bpf_dtab_netdev *dst)
 {
 	struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
 	struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq);
@@ -423,6 +477,14 @@  static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
 	if (!bq->dev_rx)
 		bq->dev_rx = dev_rx;
 
+	/* Store (potential) xdp_prog that run before egress to dev as
+	 * part of bulk_queue.  This will be same xdp_prog for all
+	 * xdp_frame's in bulk_queue, because this per-CPU store must
+	 * be flushed from net_device drivers NAPI func end.
+	 */
+	if (dst && dst->xdp_prog && !bq->xdp_prog)
+		bq->xdp_prog = dst->xdp_prog;
+
 	bq->q[bq->count++] = xdpf;
 
 	if (!bq->flush_node.prev)
@@ -430,7 +492,8 @@  static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
 }
 
 static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
-			       struct net_device *dev_rx)
+				struct net_device *dev_rx,
+				struct bpf_dtab_netdev *dst)
 {
 	struct xdp_frame *xdpf;
 	int err;
@@ -446,42 +509,14 @@  static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
 	if (unlikely(!xdpf))
 		return -EOVERFLOW;
 
-	bq_enqueue(dev, xdpf, dev_rx);
+	bq_enqueue(dev, xdpf, dev_rx, dst);
 	return 0;
 }
 
-static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
-					 struct xdp_buff *xdp,
-					 struct bpf_prog *xdp_prog)
-{
-	struct xdp_txq_info txq = { .dev = dev };
-	u32 act;
-
-	xdp_set_data_meta_invalid(xdp);
-	xdp->txq = &txq;
-
-	act = bpf_prog_run_xdp(xdp_prog, xdp);
-	switch (act) {
-	case XDP_PASS:
-		return xdp;
-	case XDP_DROP:
-		break;
-	default:
-		bpf_warn_invalid_xdp_action(act);
-		fallthrough;
-	case XDP_ABORTED:
-		trace_xdp_exception(dev, xdp_prog, act);
-		break;
-	}
-
-	xdp_return_buff(xdp);
-	return NULL;
-}
-
 int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
 		    struct net_device *dev_rx)
 {
-	return __xdp_enqueue(dev, xdp, dev_rx);
+	return __xdp_enqueue(dev, xdp, dev_rx, NULL);
 }
 
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
@@ -489,12 +524,7 @@  int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 {
 	struct net_device *dev = dst->dev;
 
-	if (dst->xdp_prog) {
-		xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog);
-		if (!xdp)
-			return 0;
-	}
-	return __xdp_enqueue(dev, xdp, dev_rx);
+	return __xdp_enqueue(dev, xdp, dev_rx, dst);
 }
 
 int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,