[bpf-next V5 PATCH 0/8] xdp: introduce bulking for ndo_xdp_xmit API

[bpf-next V5 PATCH 0/8] xdp: introduce bulking for ndo_xdp_xmit API

[Jesper Dangaard Brouer]

This patchset change ndo_xdp_xmit API to take a bulk of xdp frames.

When kernel is compiled with CONFIG_RETPOLINE, every indirect function
pointer (branch) call hurts performance. For XDP this have a huge
negative performance impact.

This patchset reduce the needed (indirect) calls to ndo_xdp_xmit, but
also prepares for further optimizations.  The DMA APIs use of indirect
function pointer calls is the primary source the regression.  It is
left for a followup patchset, to use bulking calls towards the DMA API
(via the scatter-gatter calls).

The other advantage of this API change is that drivers can easier
amortize the cost of any sync/locking scheme, over the bulk of
packets.  The assumption of the current API is that the driver
implemementing the NDO will also allocate a dedicated XDP TX queue for
every CPU in the system.  Which is not always possible or practical to
configure. E.g. ixgbe cannot load an XDP program on a machine with
more than 96 CPUs, due to limited hardware TX queues.  E.g. virtio_net
is hard to configure as it requires manually increasing the
queues. E.g. tun driver chooses to use a per XDP frame producer lock
modulo smp_processor_id over avail queues.

I'm considered adding 'flags' to ndo_xdp_xmit, but it's not part of
this patchset.  This will be a followup patchset, once we know if this
will be needed (e.g. for non-map xdp_redirect flush-flag, and if
AF_XDP chooses to use ndo_xdp_xmit for TX).

---
V5: Fixed up issues spotted by Daniel and John

V4: Splitout the patches from 4 to 8 patches.  I cannot split the
driver changes from the NDO change, but I've tried to isolated the NDO
change together with the driver change as much as possible.


Jesper Dangaard Brouer (8):
      bpf: devmap introduce dev_map_enqueue
      bpf: devmap prepare xdp frames for bulking
      xdp: add tracepoint for devmap like cpumap have
      samples/bpf: xdp_monitor use tracepoint xdp:xdp_devmap_xmit
      xdp: introduce xdp_return_frame_rx_napi
      xdp: change ndo_xdp_xmit API to support bulking
      xdp/trace: extend tracepoint in devmap with an err
      samples/bpf: xdp_monitor use err code from tracepoint xdp:xdp_devmap_xmit


 drivers/net/ethernet/intel/i40e/i40e_txrx.c   |   26 ++++-
 drivers/net/ethernet/intel/i40e/i40e_txrx.h   |    2 
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   21 +++-
 drivers/net/tun.c                             |   37 +++++--
 drivers/net/virtio_net.c                      |   66 +++++++++----
 include/linux/bpf.h                           |   18 +++
 include/linux/netdevice.h                     |   14 ++-
 include/net/page_pool.h                       |    5 +
 include/net/xdp.h                             |    1 
 include/trace/events/xdp.h                    |   50 +++++++++-
 kernel/bpf/cpumap.c                           |    2 
 kernel/bpf/devmap.c                           |  131 +++++++++++++++++++++++--
 net/core/filter.c                             |   23 +---
 net/core/xdp.c                                |   20 +++-
 samples/bpf/xdp_monitor_kern.c                |   49 +++++++++
 samples/bpf/xdp_monitor_user.c                |   69 +++++++++++++
 16 files changed, 448 insertions(+), 86 deletions(-)

[bpf-next V5 PATCH 1/8] bpf: devmap introduce dev_map_enqueue

[Jesper Dangaard Brouer]

Functionality is the same, but the ndo_xdp_xmit call is now
simply invoked from inside the devmap.c code.

V2: Fix compile issue reported by kbuild test robot <lkp@intel.com>

V5: Cleanups requested by Daniel
 - Newlines before func definition
 - Use BUILD_BUG_ON checks
 - Remove unnecessary use return value store in dev_map_enqueue

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/linux/bpf.h        |   16 +++++++++++++---
 include/trace/events/xdp.h |    9 ++++++++-
 kernel/bpf/devmap.c        |   34 ++++++++++++++++++++++++++++------
 net/core/filter.c          |   15 ++-------------
 4 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1795eeee846c..23a809da452d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -487,14 +487,16 @@ int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
 
 /* Map specifics */
-struct net_device  *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
+struct xdp_buff;
+
+struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
 void __dev_map_insert_ctx(struct bpf_map *map, u32 index);
 void __dev_map_flush(struct bpf_map *map);
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp);
 
 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key);
 void __cpu_map_insert_ctx(struct bpf_map *map, u32 index);
 void __cpu_map_flush(struct bpf_map *map);
-struct xdp_buff;
 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
 
@@ -573,6 +575,15 @@ static inline void __dev_map_flush(struct bpf_map *map)
 {
 }
 
+struct xdp_buff;
+struct bpf_dtab_netdev;
+
+static inline
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
+{
+	return 0;
+}
+
 static inline
 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
 {
@@ -587,7 +598,6 @@ static inline void __cpu_map_flush(struct bpf_map *map)
 {
 }
 
-struct xdp_buff;
 static inline int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu,
 				  struct xdp_buff *xdp,
 				  struct net_device *dev_rx)
diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 8989a92c571a..96104610d40e 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -138,11 +138,18 @@ DEFINE_EVENT_PRINT(xdp_redirect_template, xdp_redirect_map_err,
 		  __entry->map_id, __entry->map_index)
 );
 
+#ifndef __DEVMAP_OBJ_TYPE
+#define __DEVMAP_OBJ_TYPE
+struct _bpf_dtab_netdev {
+	struct net_device *dev;
+};
+#endif /* __DEVMAP_OBJ_TYPE */
+
 #define devmap_ifindex(fwd, map)				\
 	(!fwd ? 0 :						\
 	 (!map ? 0 :						\
 	  ((map->map_type == BPF_MAP_TYPE_DEVMAP) ?		\
-	   ((struct net_device *)fwd)->ifindex : 0)))
+	   ((struct _bpf_dtab_netdev *)fwd)->dev->ifindex : 0)))
 
 #define _trace_xdp_redirect_map(dev, xdp, fwd, map, idx)		\
 	 trace_xdp_redirect_map(dev, xdp, devmap_ifindex(fwd, map),	\
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 565f9ece9115..06c400e7e4ff 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -48,13 +48,15 @@
  * calls will fail at this point.
  */
 #include <linux/bpf.h>
+#include <net/xdp.h>
 #include <linux/filter.h>
+#include <trace/events/xdp.h>
 
 #define DEV_CREATE_FLAG_MASK \
 	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
 
 struct bpf_dtab_netdev {
-	struct net_device *dev;
+	struct net_device *dev; /* must be first member, due to tracepoint */
 	struct bpf_dtab *dtab;
 	unsigned int bit;
 	struct rcu_head rcu;
@@ -240,21 +242,38 @@ void __dev_map_flush(struct bpf_map *map)
  * update happens in parallel here a dev_put wont happen until after reading the
  * ifindex.
  */
-struct net_device  *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
+struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
-	struct bpf_dtab_netdev *dev;
+	struct bpf_dtab_netdev *obj;
 
 	if (key >= map->max_entries)
 		return NULL;
 
-	dev = READ_ONCE(dtab->netdev_map[key]);
-	return dev ? dev->dev : NULL;
+	obj = READ_ONCE(dtab->netdev_map[key]);
+	return obj;
+}
+
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
+{
+	struct net_device *dev = dst->dev;
+	struct xdp_frame *xdpf;
+
+	if (!dev->netdev_ops->ndo_xdp_xmit)
+		return -EOPNOTSUPP;
+
+	xdpf = convert_to_xdp_frame(xdp);
+	if (unlikely(!xdpf))
+		return -EOVERFLOW;
+
+	/* TODO: implement a bulking/enqueue step later */
+	return dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
 }
 
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
-	struct net_device *dev = __dev_map_lookup_elem(map, *(u32 *)key);
+	struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
+	struct net_device *dev = dev = obj ? obj->dev : NULL;
 
 	return dev ? &dev->ifindex : NULL;
 }
@@ -405,6 +424,9 @@ static struct notifier_block dev_map_notifier = {
 
 static int __init dev_map_init(void)
 {
+	/* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
+	BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
+		     offsetof(struct _bpf_dtab_netdev, dev));
 	register_netdevice_notifier(&dev_map_notifier);
 	return 0;
 }
diff --git a/net/core/filter.c b/net/core/filter.c
index aa114c4acb25..c867106d3707 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3065,20 +3065,9 @@ static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
 
 	switch (map->map_type) {
 	case BPF_MAP_TYPE_DEVMAP: {
-		struct net_device *dev = fwd;
-		struct xdp_frame *xdpf;
+		struct bpf_dtab_netdev *dst = fwd;
 
-		if (!dev->netdev_ops->ndo_xdp_xmit)
-			return -EOPNOTSUPP;
-
-		xdpf = convert_to_xdp_frame(xdp);
-		if (unlikely(!xdpf))
-			return -EOVERFLOW;
-
-		/* TODO: move to inside map code instead, for bulk support
-		 * err = dev_map_enqueue(dev, xdp);
-		 */
-		err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
+		err = dev_map_enqueue(dst, xdp);
 		if (err)
 			return err;
 		__dev_map_insert_ctx(map, index);

[bpf-next V5 PATCH 2/8] bpf: devmap prepare xdp frames for bulking

[Jesper Dangaard Brouer]

Like cpumap create queue for xdp frames that will be bulked.  For now,
this patch simply invoke ndo_xdp_xmit foreach frame.  This happens,
either when the map flush operation is envoked, or when the limit
DEV_MAP_BULK_SIZE is reached.

V5: Avoid memleak on error path in dev_map_update_elem()

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 kernel/bpf/devmap.c |   74 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 06c400e7e4ff..15293b9dfb77 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -55,10 +55,17 @@
 #define DEV_CREATE_FLAG_MASK \
 	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
 
+#define DEV_MAP_BULK_SIZE 16
+struct xdp_bulk_queue {
+	struct xdp_frame *q[DEV_MAP_BULK_SIZE];
+	unsigned int count;
+};
+
 struct bpf_dtab_netdev {
 	struct net_device *dev; /* must be first member, due to tracepoint */
 	struct bpf_dtab *dtab;
 	unsigned int bit;
+	struct xdp_bulk_queue __percpu *bulkq;
 	struct rcu_head rcu;
 };
 
@@ -208,6 +215,34 @@ void __dev_map_insert_ctx(struct bpf_map *map, u32 bit)
 	__set_bit(bit, bitmap);
 }
 
+static int bq_xmit_all(struct bpf_dtab_netdev *obj,
+			 struct xdp_bulk_queue *bq)
+{
+	struct net_device *dev = obj->dev;
+	int i;
+
+	if (unlikely(!bq->count))
+		return 0;
+
+	for (i = 0; i < bq->count; i++) {
+		struct xdp_frame *xdpf = bq->q[i];
+
+		prefetch(xdpf);
+	}
+
+	for (i = 0; i < bq->count; i++) {
+		struct xdp_frame *xdpf = bq->q[i];
+		int err;
+
+		err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
+		if (err)
+			xdp_return_frame(xdpf);
+	}
+	bq->count = 0;
+
+	return 0;
+}
+
 /* __dev_map_flush is called from xdp_do_flush_map() which _must_ be signaled
  * from the driver before returning from its napi->poll() routine. The poll()
  * routine is called either from busy_poll context or net_rx_action signaled
@@ -223,6 +258,7 @@ void __dev_map_flush(struct bpf_map *map)
 
 	for_each_set_bit(bit, bitmap, map->max_entries) {
 		struct bpf_dtab_netdev *dev = READ_ONCE(dtab->netdev_map[bit]);
+		struct xdp_bulk_queue *bq;
 		struct net_device *netdev;
 
 		/* This is possible if the dev entry is removed by user space
@@ -232,6 +268,9 @@ void __dev_map_flush(struct bpf_map *map)
 			continue;
 
 		__clear_bit(bit, bitmap);
+
+		bq = this_cpu_ptr(dev->bulkq);
+		bq_xmit_all(dev, bq);
 		netdev = dev->dev;
 		if (likely(netdev->netdev_ops->ndo_xdp_flush))
 			netdev->netdev_ops->ndo_xdp_flush(netdev);
@@ -254,6 +293,20 @@ struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
 	return obj;
 }
 
+/* Runs under RCU-read-side, plus in softirq under NAPI protection.
+ * Thus, safe percpu variable access.
+ */
+static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf)
+{
+	struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
+
+	if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
+		bq_xmit_all(obj, bq);
+
+	bq->q[bq->count++] = xdpf;
+	return 0;
+}
+
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
 {
 	struct net_device *dev = dst->dev;
@@ -266,8 +319,7 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
 	if (unlikely(!xdpf))
 		return -EOVERFLOW;
 
-	/* TODO: implement a bulking/enqueue step later */
-	return dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
+	return bq_enqueue(dst, xdpf);
 }
 
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
@@ -282,13 +334,18 @@ static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
 {
 	if (dev->dev->netdev_ops->ndo_xdp_flush) {
 		struct net_device *fl = dev->dev;
+		struct xdp_bulk_queue *bq;
 		unsigned long *bitmap;
+
 		int cpu;
 
 		for_each_online_cpu(cpu) {
 			bitmap = per_cpu_ptr(dev->dtab->flush_needed, cpu);
 			__clear_bit(dev->bit, bitmap);
 
+			bq = per_cpu_ptr(dev->bulkq, cpu);
+			bq_xmit_all(dev, bq);
+
 			fl->netdev_ops->ndo_xdp_flush(dev->dev);
 		}
 	}
@@ -300,6 +357,7 @@ static void __dev_map_entry_free(struct rcu_head *rcu)
 
 	dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
 	dev_map_flush_old(dev);
+	free_percpu(dev->bulkq);
 	dev_put(dev->dev);
 	kfree(dev);
 }
@@ -332,6 +390,7 @@ static int dev_map_update_elem(struct bpf_map *map, void *key, void *value,
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
 	struct net *net = current->nsproxy->net_ns;
+	gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN;
 	struct bpf_dtab_netdev *dev, *old_dev;
 	u32 i = *(u32 *)key;
 	u32 ifindex = *(u32 *)value;
@@ -346,13 +405,20 @@ static int dev_map_update_elem(struct bpf_map *map, void *key, void *value,
 	if (!ifindex) {
 		dev = NULL;
 	} else {
-		dev = kmalloc_node(sizeof(*dev), GFP_ATOMIC | __GFP_NOWARN,
-				   map->numa_node);
+		dev = kmalloc_node(sizeof(*dev), gfp, map->numa_node);
 		if (!dev)
 			return -ENOMEM;
 
+		dev->bulkq = __alloc_percpu_gfp(sizeof(*dev->bulkq),
+						sizeof(void *), gfp);
+		if (!dev->bulkq) {
+			kfree(dev);
+			return -ENOMEM;
+		}
+
 		dev->dev = dev_get_by_index(net, ifindex);
 		if (!dev->dev) {
+			free_percpu(dev->bulkq);
 			kfree(dev);
 			return -EINVAL;
 		}

[bpf-next V5 PATCH 3/8] xdp: add tracepoint for devmap like cpumap have

[Jesper Dangaard Brouer]

Notice how this allow us get XDP statistic without affecting the XDP
performance, as tracepoint is no-longer activated on a per packet basis.

V5: Spotted by John Fastabend.
 Fix 'sent' also counted 'drops' in this patch, a later patch corrected
 this, but it was a mistake in this intermediate step.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/linux/bpf.h        |    6 ++++--
 include/trace/events/xdp.h |   39 +++++++++++++++++++++++++++++++++++++++
 kernel/bpf/devmap.c        |   27 +++++++++++++++++++++++----
 net/core/filter.c          |    2 +-
 4 files changed, 67 insertions(+), 7 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 23a809da452d..bbe297436e5d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -492,7 +492,8 @@ struct xdp_buff;
 struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
 void __dev_map_insert_ctx(struct bpf_map *map, u32 index);
 void __dev_map_flush(struct bpf_map *map);
-int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp);
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
+		    struct net_device *dev_rx);
 
 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key);
 void __cpu_map_insert_ctx(struct bpf_map *map, u32 index);
@@ -579,7 +580,8 @@ struct xdp_buff;
 struct bpf_dtab_netdev;
 
 static inline
-int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
+		    struct net_device *dev_rx)
 {
 	return 0;
 }
diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 96104610d40e..2e9ef0650144 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -229,6 +229,45 @@ TRACE_EVENT(xdp_cpumap_enqueue,
 		  __entry->to_cpu)
 );
 
+TRACE_EVENT(xdp_devmap_xmit,
+
+	TP_PROTO(const struct bpf_map *map, u32 map_index,
+		 int sent, int drops,
+		 const struct net_device *from_dev,
+		 const struct net_device *to_dev),
+
+	TP_ARGS(map, map_index, sent, drops, from_dev, to_dev),
+
+	TP_STRUCT__entry(
+		__field(int, map_id)
+		__field(u32, act)
+		__field(u32, map_index)
+		__field(int, drops)
+		__field(int, sent)
+		__field(int, from_ifindex)
+		__field(int, to_ifindex)
+	),
+
+	TP_fast_assign(
+		__entry->map_id		= map->id;
+		__entry->act		= XDP_REDIRECT;
+		__entry->map_index	= map_index;
+		__entry->drops		= drops;
+		__entry->sent		= sent;
+		__entry->from_ifindex	= from_dev->ifindex;
+		__entry->to_ifindex	= to_dev->ifindex;
+	),
+
+	TP_printk("ndo_xdp_xmit"
+		  " map_id=%d map_index=%d action=%s"
+		  " sent=%d drops=%d"
+		  " from_ifindex=%d to_ifindex=%d",
+		  __entry->map_id, __entry->map_index,
+		  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
+		  __entry->sent, __entry->drops,
+		  __entry->from_ifindex, __entry->to_ifindex)
+);
+
 #endif /* _TRACE_XDP_H */
 
 #include <trace/define_trace.h>
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 15293b9dfb77..ff2f3bf59f2f 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -58,6 +58,7 @@
 #define DEV_MAP_BULK_SIZE 16
 struct xdp_bulk_queue {
 	struct xdp_frame *q[DEV_MAP_BULK_SIZE];
+	struct net_device *dev_rx;
 	unsigned int count;
 };
 
@@ -219,6 +220,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 			 struct xdp_bulk_queue *bq)
 {
 	struct net_device *dev = obj->dev;
+	int sent = 0, drops = 0;
 	int i;
 
 	if (unlikely(!bq->count))
@@ -235,11 +237,18 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 		int err;
 
 		err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
-		if (err)
+		if (err) {
+			drops++;
 			xdp_return_frame(xdpf);
+		} else {
+			sent++;
+		}
 	}
 	bq->count = 0;
 
+	trace_xdp_devmap_xmit(&obj->dtab->map, obj->bit,
+			      sent, drops, bq->dev_rx, dev);
+	bq->dev_rx = NULL;
 	return 0;
 }
 
@@ -296,18 +305,28 @@ struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
  * Thus, safe percpu variable access.
  */
-static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf)
+static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
+		      struct net_device *dev_rx)
+
 {
 	struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
 
 	if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
 		bq_xmit_all(obj, bq);
 
+	/* Ingress dev_rx will be the same for all xdp_frame's in
+	 * bulk_queue, because bq stored per-CPU and must be flushed
+	 * from net_device drivers NAPI func end.
+	 */
+	if (!bq->dev_rx)
+		bq->dev_rx = dev_rx;
+
 	bq->q[bq->count++] = xdpf;
 	return 0;
 }
 
-int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
+		    struct net_device *dev_rx)
 {
 	struct net_device *dev = dst->dev;
 	struct xdp_frame *xdpf;
@@ -319,7 +338,7 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp)
 	if (unlikely(!xdpf))
 		return -EOVERFLOW;
 
-	return bq_enqueue(dst, xdpf);
+	return bq_enqueue(dst, xdpf, dev_rx);
 }
 
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
diff --git a/net/core/filter.c b/net/core/filter.c
index c867106d3707..36cf2f87d742 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3067,7 +3067,7 @@ static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
 	case BPF_MAP_TYPE_DEVMAP: {
 		struct bpf_dtab_netdev *dst = fwd;
 
-		err = dev_map_enqueue(dst, xdp);
+		err = dev_map_enqueue(dst, xdp, dev_rx);
 		if (err)
 			return err;
 		__dev_map_insert_ctx(map, index);

[bpf-next V5 PATCH 4/8] samples/bpf: xdp_monitor use tracepoint xdp:xdp_devmap_xmit

[Jesper Dangaard Brouer]

The xdp_monitor sample/tool is updated to use the new tracepoint
xdp:xdp_devmap_xmit the previous patch just introduced.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 samples/bpf/xdp_monitor_kern.c |   39 +++++++++++++++++++++++++++++++++++
 samples/bpf/xdp_monitor_user.c |   44 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/samples/bpf/xdp_monitor_kern.c b/samples/bpf/xdp_monitor_kern.c
index 211db8ded0de..2854aa0665ea 100644
--- a/samples/bpf/xdp_monitor_kern.c
+++ b/samples/bpf/xdp_monitor_kern.c
@@ -208,3 +208,42 @@ int trace_xdp_cpumap_kthread(struct cpumap_kthread_ctx *ctx)
 
 	return 0;
 }
+
+struct bpf_map_def SEC("maps") devmap_xmit_cnt = {
+	.type		= BPF_MAP_TYPE_PERCPU_ARRAY,
+	.key_size	= sizeof(u32),
+	.value_size	= sizeof(struct datarec),
+	.max_entries	= 1,
+};
+
+/* Tracepoint: /sys/kernel/debug/tracing/events/xdp/xdp_devmap_xmit/format
+ * Code in:         kernel/include/trace/events/xdp.h
+ */
+struct devmap_xmit_ctx {
+	u64 __pad;		// First 8 bytes are not accessible by bpf code
+	int map_id;		//	offset:8;  size:4; signed:1;
+	u32 act;		//	offset:12; size:4; signed:0;
+	u32 map_index;		//	offset:16; size:4; signed:0;
+	int drops;		//	offset:20; size:4; signed:1;
+	int sent;		//	offset:24; size:4; signed:1;
+	int from_ifindex;	//	offset:28; size:4; signed:1;
+	int to_ifindex;		//	offset:32; size:4; signed:1;
+};
+
+SEC("tracepoint/xdp/xdp_devmap_xmit")
+int trace_xdp_devmap_xmit(struct devmap_xmit_ctx *ctx)
+{
+	struct datarec *rec;
+	u32 key = 0;
+
+	rec = bpf_map_lookup_elem(&devmap_xmit_cnt, &key);
+	if (!rec)
+		return 0;
+	rec->processed += ctx->sent;
+	rec->dropped   += ctx->drops;
+
+	/* Record bulk events, then userspace can calc average bulk size */
+	rec->info += 1;
+
+	return 1;
+}
diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index bf09b5188acd..7e18a454924c 100644
--- a/samples/bpf/xdp_monitor_user.c
+++ b/samples/bpf/xdp_monitor_user.c
@@ -141,6 +141,7 @@ struct stats_record {
 	struct record_u64 xdp_exception[XDP_ACTION_MAX];
 	struct record xdp_cpumap_kthread;
 	struct record xdp_cpumap_enqueue[MAX_CPUS];
+	struct record xdp_devmap_xmit;
 };
 
 static bool map_collect_record(int fd, __u32 key, struct record *rec)
@@ -397,7 +398,7 @@ static void stats_print(struct stats_record *stats_rec,
 			info = calc_info(r, p, t);
 			if (info > 0)
 				i_str = "sched";
-			if (pps > 0)
+			if (pps > 0 || drop > 0)
 				printf(fmt1, "cpumap-kthread",
 				       i, pps, drop, info, i_str);
 		}
@@ -409,6 +410,42 @@ static void stats_print(struct stats_record *stats_rec,
 		printf(fmt2, "cpumap-kthread", "total", pps, drop, info, i_str);
 	}
 
+	/* devmap ndo_xdp_xmit stats */
+	{
+		char *fmt1 = "%-15s %-7d %'-12.0f %'-12.0f %'-10.2f %s\n";
+		char *fmt2 = "%-15s %-7s %'-12.0f %'-12.0f %'-10.2f %s\n";
+		struct record *rec, *prev;
+		double drop, info;
+		char *i_str = "";
+
+		rec  =  &stats_rec->xdp_devmap_xmit;
+		prev = &stats_prev->xdp_devmap_xmit;
+		t = calc_period(rec, prev);
+		for (i = 0; i < nr_cpus; i++) {
+			struct datarec *r = &rec->cpu[i];
+			struct datarec *p = &prev->cpu[i];
+
+			pps  = calc_pps(r, p, t);
+			drop = calc_drop(r, p, t);
+			info = calc_info(r, p, t);
+			if (info > 0) {
+				i_str = "bulk-average";
+				info = (pps+drop) / info; /* calc avg bulk */
+			}
+			if (pps > 0 || drop > 0)
+				printf(fmt1, "devmap-xmit",
+				       i, pps, drop, info, i_str);
+		}
+		pps = calc_pps(&rec->total, &prev->total, t);
+		drop = calc_drop(&rec->total, &prev->total, t);
+		info = calc_info(&rec->total, &prev->total, t);
+		if (info > 0) {
+			i_str = "bulk-average";
+			info = (pps+drop) / info; /* calc avg bulk */
+		}
+		printf(fmt2, "devmap-xmit", "total", pps, drop, info, i_str);
+	}
+
 	printf("\n");
 }
 
@@ -437,6 +474,9 @@ static bool stats_collect(struct stats_record *rec)
 	fd = map_data[3].fd; /* map3: cpumap_kthread_cnt */
 	map_collect_record(fd, 0, &rec->xdp_cpumap_kthread);
 
+	fd = map_data[4].fd; /* map4: devmap_xmit_cnt */
+	map_collect_record(fd, 0, &rec->xdp_devmap_xmit);
+
 	return true;
 }
 
@@ -480,6 +520,7 @@ static struct stats_record *alloc_stats_record(void)
 
 	rec_sz = sizeof(struct datarec);
 	rec->xdp_cpumap_kthread.cpu = alloc_rec_per_cpu(rec_sz);
+	rec->xdp_devmap_xmit.cpu    = alloc_rec_per_cpu(rec_sz);
 
 	for (i = 0; i < MAX_CPUS; i++)
 		rec->xdp_cpumap_enqueue[i].cpu = alloc_rec_per_cpu(rec_sz);
@@ -498,6 +539,7 @@ static void free_stats_record(struct stats_record *r)
 		free(r->xdp_exception[i].cpu);
 
 	free(r->xdp_cpumap_kthread.cpu);
+	free(r->xdp_devmap_xmit.cpu);
 
 	for (i = 0; i < MAX_CPUS; i++)
 		free(r->xdp_cpumap_enqueue[i].cpu);

[bpf-next V5 PATCH 5/8] xdp: introduce xdp_return_frame_rx_napi

[Jesper Dangaard Brouer]

When sending an xdp_frame through xdp_do_redirect call, then error
cases can happen where the xdp_frame needs to be dropped, and
returning an -errno code isn't sufficient/possible any-longer
(e.g. for cpumap case). This is already fully supported, by simply
calling xdp_return_frame.

This patch is an optimization, which provides xdp_return_frame_rx_napi,
which is a faster variant for these error cases.  It take advantage of
the protection provided by XDP RX running under NAPI protection.

This change is mostly relevant for drivers using the page_pool
allocator as it can take advantage of this. (Tested with mlx5).

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/net/page_pool.h |    5 +++--
 include/net/xdp.h       |    1 +
 kernel/bpf/cpumap.c     |    2 +-
 kernel/bpf/devmap.c     |    2 +-
 net/core/xdp.c          |   20 ++++++++++++++++----
 5 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index c79087153148..694d055e01ef 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -115,13 +115,14 @@ void page_pool_destroy(struct page_pool *pool);
 void __page_pool_put_page(struct page_pool *pool,
 			  struct page *page, bool allow_direct);
 
-static inline void page_pool_put_page(struct page_pool *pool, struct page *page)
+static inline void page_pool_put_page(struct page_pool *pool,
+				      struct page *page, bool allow_direct)
 {
 	/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
 	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
 	 */
 #ifdef CONFIG_PAGE_POOL
-	__page_pool_put_page(pool, page, false);
+	__page_pool_put_page(pool, page, allow_direct);
 #endif
 }
 /* Very limited use-cases allow recycle direct */
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 0b689cf561c7..7ad779237ae8 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -104,6 +104,7 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
 }
 
 void xdp_return_frame(struct xdp_frame *xdpf);
+void xdp_return_frame_rx_napi(struct xdp_frame *xdpf);
 void xdp_return_buff(struct xdp_buff *xdp);
 
 int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index c95b04ec103e..e0918d180f08 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -578,7 +578,7 @@ static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
 		err = __ptr_ring_produce(q, xdpf);
 		if (err) {
 			drops++;
-			xdp_return_frame(xdpf);
+			xdp_return_frame_rx_napi(xdpf);
 		}
 		processed++;
 	}
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index ff2f3bf59f2f..a9cd5c93dd2b 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -239,7 +239,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 		err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
 		if (err) {
 			drops++;
-			xdp_return_frame(xdpf);
+			xdp_return_frame_rx_napi(xdpf);
 		} else {
 			sent++;
 		}
diff --git a/net/core/xdp.c b/net/core/xdp.c
index bf6758f74339..cb8c4e061a5a 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -308,7 +308,13 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
 }
 EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);
 
-static void xdp_return(void *data, struct xdp_mem_info *mem)
+/* XDP RX runs under NAPI protection, and in different delivery error
+ * scenarios (e.g. queue full), it is possible to return the xdp_frame
+ * while still leveraging this protection.  The @napi_direct boolian
+ * is used for those calls sites.  Thus, allowing for faster recycling
+ * of xdp_frames/pages in those cases.
+ */
+static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct)
 {
 	struct xdp_mem_allocator *xa;
 	struct page *page;
@@ -320,7 +326,7 @@ static void xdp_return(void *data, struct xdp_mem_info *mem)
 		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
 		page = virt_to_head_page(data);
 		if (xa)
-			page_pool_put_page(xa->page_pool, page);
+			page_pool_put_page(xa->page_pool, page, napi_direct);
 		else
 			put_page(page);
 		rcu_read_unlock();
@@ -340,12 +346,18 @@ static void xdp_return(void *data, struct xdp_mem_info *mem)
 
 void xdp_return_frame(struct xdp_frame *xdpf)
 {
-	xdp_return(xdpf->data, &xdpf->mem);
+	__xdp_return(xdpf->data, &xdpf->mem, false);
 }
 EXPORT_SYMBOL_GPL(xdp_return_frame);
 
+void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
+{
+	__xdp_return(xdpf->data, &xdpf->mem, true);
+}
+EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
+
 void xdp_return_buff(struct xdp_buff *xdp)
 {
-	xdp_return(xdp->data, &xdp->rxq->mem);
+	__xdp_return(xdp->data, &xdp->rxq->mem, true);
 }
 EXPORT_SYMBOL_GPL(xdp_return_buff);

[bpf-next V5 PATCH 6/8] xdp: change ndo_xdp_xmit API to support bulking

[Jesper Dangaard Brouer]

This patch change the API for ndo_xdp_xmit to support bulking
xdp_frames.

When kernel is compiled with CONFIG_RETPOLINE, XDP sees a huge slowdown.
Most of the slowdown is caused by DMA API indirect function calls, but
also the net_device->ndo_xdp_xmit() call.

Benchmarked patch with CONFIG_RETPOLINE, using xdp_redirect_map with
single flow/core test (CPU E5-1650 v4 @ 3.60GHz), showed
performance improved:
 for driver ixgbe: 6,042,682 pps -> 6,853,768 pps = +811,086 pps
 for driver i40e : 6,187,169 pps -> 6,724,519 pps = +537,350 pps

With frames avail as a bulk inside the driver ndo_xdp_xmit call,
further optimizations are possible, like bulk DMA-mapping for TX.

Testing without CONFIG_RETPOLINE show the same performance for
physical NIC drivers.

The virtual NIC driver tun sees a huge performance boost, as it can
avoid doing per frame producer locking, but instead amortize the
locking cost over the bulk.

V2: Fix compile errors reported by kbuild test robot <lkp@intel.com>
V4: Isolated ndo, driver changes and callers.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   |   26 +++++++---
 drivers/net/ethernet/intel/i40e/i40e_txrx.h   |    2 -
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   21 ++++++--
 drivers/net/tun.c                             |   37 +++++++++-----
 drivers/net/virtio_net.c                      |   66 +++++++++++++++++++------
 include/linux/netdevice.h                     |   14 +++--
 kernel/bpf/devmap.c                           |   29 +++++++----
 net/core/filter.c                             |    8 ++-
 8 files changed, 139 insertions(+), 64 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 5efa68de935b..9b698c5acd05 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -3664,14 +3664,19 @@ netdev_tx_t i40e_lan_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
  * @dev: netdev
  * @xdp: XDP buffer
  *
- * Returns Zero if sent, else an error code
+ * Returns number of frames successfully sent. Frames that fail are
+ * free'ed via XDP return API.
+ *
+ * For error cases, a negative errno code is returned and no-frames
+ * are transmitted (caller must handle freeing frames).
  **/
-int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+int i40e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames)
 {
 	struct i40e_netdev_priv *np = netdev_priv(dev);
 	unsigned int queue_index = smp_processor_id();
 	struct i40e_vsi *vsi = np->vsi;
-	int err;
+	int drops = 0;
+	int i;
 
 	if (test_bit(__I40E_VSI_DOWN, vsi->state))
 		return -ENETDOWN;
@@ -3679,11 +3684,18 @@ int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
 	if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs)
 		return -ENXIO;
 
-	err = i40e_xmit_xdp_ring(xdpf, vsi->xdp_rings[queue_index]);
-	if (err != I40E_XDP_TX)
-		return -ENOSPC;
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdpf = frames[i];
+		int err;
 
-	return 0;
+		err = i40e_xmit_xdp_ring(xdpf, vsi->xdp_rings[queue_index]);
+		if (err != I40E_XDP_TX) {
+			xdp_return_frame_rx_napi(xdpf);
+			drops++;
+		}
+	}
+
+	return n - drops;
 }
 
 /**
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index fdd2c55f03a6..eb8804b3d7b6 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -487,7 +487,7 @@ u32 i40e_get_tx_pending(struct i40e_ring *ring, bool in_sw);
 void i40e_detect_recover_hung(struct i40e_vsi *vsi);
 int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
 bool __i40e_chk_linearize(struct sk_buff *skb);
-int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf);
+int i40e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames);
 void i40e_xdp_flush(struct net_device *dev);
 
 /**
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 6652b201df5b..9645619f7729 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -10017,11 +10017,13 @@ static int ixgbe_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }
 
-static int ixgbe_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+static int ixgbe_xdp_xmit(struct net_device *dev, int n,
+			  struct xdp_frame **frames)
 {
 	struct ixgbe_adapter *adapter = netdev_priv(dev);
 	struct ixgbe_ring *ring;
-	int err;
+	int drops = 0;
+	int i;
 
 	if (unlikely(test_bit(__IXGBE_DOWN, &adapter->state)))
 		return -ENETDOWN;
@@ -10033,11 +10035,18 @@ static int ixgbe_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
 	if (unlikely(!ring))
 		return -ENXIO;
 
-	err = ixgbe_xmit_xdp_ring(adapter, xdpf);
-	if (err != IXGBE_XDP_TX)
-		return -ENOSPC;
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdpf = frames[i];
+		int err;
 
-	return 0;
+		err = ixgbe_xmit_xdp_ring(adapter, xdpf);
+		if (err != IXGBE_XDP_TX) {
+			xdp_return_frame_rx_napi(xdpf);
+			drops++;
+		}
+	}
+
+	return n - drops;
 }
 
 static void ixgbe_xdp_flush(struct net_device *dev)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 44d4f3d25350..d3dcfcb1c4b3 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -70,6 +70,7 @@
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
 #include <net/sock.h>
+#include <net/xdp.h>
 #include <linux/seq_file.h>
 #include <linux/uio.h>
 #include <linux/skb_array.h>
@@ -1290,34 +1291,44 @@ static const struct net_device_ops tun_netdev_ops = {
 	.ndo_get_stats64	= tun_net_get_stats64,
 };
 
-static int tun_xdp_xmit(struct net_device *dev, struct xdp_frame *frame)
+static int tun_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames)
 {
 	struct tun_struct *tun = netdev_priv(dev);
 	struct tun_file *tfile;
 	u32 numqueues;
-	int ret = 0;
+	int drops = 0;
+	int cnt = n;
+	int i;
 
 	rcu_read_lock();
 
 	numqueues = READ_ONCE(tun->numqueues);
 	if (!numqueues) {
-		ret = -ENOSPC;
-		goto out;
+		rcu_read_unlock();
+		return -ENXIO; /* Caller will free/return all frames */
 	}
 
 	tfile = rcu_dereference(tun->tfiles[smp_processor_id() %
 					    numqueues]);
-	/* Encode the XDP flag into lowest bit for consumer to differ
-	 * XDP buffer from sk_buff.
-	 */
-	if (ptr_ring_produce(&tfile->tx_ring, tun_xdp_to_ptr(frame))) {
-		this_cpu_inc(tun->pcpu_stats->tx_dropped);
-		ret = -ENOSPC;
+
+	spin_lock(&tfile->tx_ring.producer_lock);
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdp = frames[i];
+		/* Encode the XDP flag into lowest bit for consumer to differ
+		 * XDP buffer from sk_buff.
+		 */
+		void *frame = tun_xdp_to_ptr(xdp);
+
+		if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
+			this_cpu_inc(tun->pcpu_stats->tx_dropped);
+			xdp_return_frame_rx_napi(xdp);
+			drops++;
+		}
 	}
+	spin_unlock(&tfile->tx_ring.producer_lock);
 
-out:
 	rcu_read_unlock();
-	return ret;
+	return cnt - drops;
 }
 
 static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
@@ -1327,7 +1338,7 @@ static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
 	if (unlikely(!frame))
 		return -EOVERFLOW;
 
-	return tun_xdp_xmit(dev, frame);
+	return tun_xdp_xmit(dev, 1, &frame);
 }
 
 static void tun_xdp_flush(struct net_device *dev)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f34794a76c4d..39a0783d1cde 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -419,23 +419,13 @@ static void virtnet_xdp_flush(struct net_device *dev)
 	virtqueue_kick(sq->vq);
 }
 
-static int __virtnet_xdp_xmit(struct virtnet_info *vi,
-			       struct xdp_frame *xdpf)
+static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
+				   struct send_queue *sq,
+				   struct xdp_frame *xdpf)
 {
 	struct virtio_net_hdr_mrg_rxbuf *hdr;
-	struct xdp_frame *xdpf_sent;
-	struct send_queue *sq;
-	unsigned int len;
-	unsigned int qp;
 	int err;
 
-	qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
-	sq = &vi->sq[qp];
-
-	/* Free up any pending old buffers before queueing new ones. */
-	while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
-		xdp_return_frame(xdpf_sent);
-
 	/* virtqueue want to use data area in-front of packet */
 	if (unlikely(xdpf->metasize > 0))
 		return -EOPNOTSUPP;
@@ -459,11 +449,40 @@ static int __virtnet_xdp_xmit(struct virtnet_info *vi,
 	return 0;
 }
 
-static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+static int __virtnet_xdp_tx_xmit(struct virtnet_info *vi,
+				   struct xdp_frame *xdpf)
+{
+	struct xdp_frame *xdpf_sent;
+	struct send_queue *sq;
+	unsigned int len;
+	unsigned int qp;
+
+	qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+	sq = &vi->sq[qp];
+
+	/* Free up any pending old buffers before queueing new ones. */
+	while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
+		xdp_return_frame(xdpf_sent);
+
+	return __virtnet_xdp_xmit_one(vi, sq, xdpf);
+}
+
+static int virtnet_xdp_xmit(struct net_device *dev,
+			    int n, struct xdp_frame **frames)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct receive_queue *rq = vi->rq;
+	struct xdp_frame *xdpf_sent;
 	struct bpf_prog *xdp_prog;
+	struct send_queue *sq;
+	unsigned int len;
+	unsigned int qp;
+	int drops = 0;
+	int err;
+	int i;
+
+	qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+	sq = &vi->sq[qp];
 
 	/* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this
 	 * indicate XDP resources have been successfully allocated.
@@ -472,7 +491,20 @@ static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
 	if (!xdp_prog)
 		return -ENXIO;
 
-	return __virtnet_xdp_xmit(vi, xdpf);
+	/* Free up any pending old buffers before queueing new ones. */
+	while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
+		xdp_return_frame(xdpf_sent);
+
+	for (i = 0; i < n; i++) {
+		struct xdp_frame *xdpf = frames[i];
+
+		err = __virtnet_xdp_xmit_one(vi, sq, xdpf);
+		if (err) {
+			xdp_return_frame_rx_napi(xdpf);
+			drops++;
+		}
+	}
+	return n - drops;
 }
 
 static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
@@ -616,7 +648,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
 			xdpf = convert_to_xdp_frame(&xdp);
 			if (unlikely(!xdpf))
 				goto err_xdp;
-			err = __virtnet_xdp_xmit(vi, xdpf);
+			err = __virtnet_xdp_tx_xmit(vi, xdpf);
 			if (unlikely(err)) {
 				trace_xdp_exception(vi->dev, xdp_prog, act);
 				goto err_xdp;
@@ -779,7 +811,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 			xdpf = convert_to_xdp_frame(&xdp);
 			if (unlikely(!xdpf))
 				goto err_xdp;
-			err = __virtnet_xdp_xmit(vi, xdpf);
+			err = __virtnet_xdp_tx_xmit(vi, xdpf);
 			if (unlikely(err)) {
 				trace_xdp_exception(vi->dev, xdp_prog, act);
 				if (unlikely(xdp_page != page))
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 03ed492c4e14..debdb6286170 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1185,9 +1185,13 @@ struct dev_ifalias {
  *	This function is used to set or query state related to XDP on the
  *	netdevice and manage BPF offload. See definition of
  *	enum bpf_netdev_command for details.
- * int (*ndo_xdp_xmit)(struct net_device *dev, struct xdp_frame *xdp);
- *	This function is used to submit a XDP packet for transmit on a
- *	netdevice.
+ * int (*ndo_xdp_xmit)(struct net_device *dev, int n, struct xdp_frame **xdp);
+ *	This function is used to submit @n XDP packets for transmit on a
+ *	netdevice. Returns number of frames successfully transmitted, frames
+ *	that got dropped are freed/returned via xdp_return_frame().
+ *	Returns negative number, means general error invoking ndo, meaning
+ *	no frames were xmit'ed and core-caller will free all frames.
+ *	TODO: Consider add flag to allow sending flush operation.
  * void (*ndo_xdp_flush)(struct net_device *dev);
  *	This function is used to inform the driver to flush a particular
  *	xdp tx queue. Must be called on same CPU as xdp_xmit.
@@ -1375,8 +1379,8 @@ struct net_device_ops {
 						       int needed_headroom);
 	int			(*ndo_bpf)(struct net_device *dev,
 					   struct netdev_bpf *bpf);
-	int			(*ndo_xdp_xmit)(struct net_device *dev,
-						struct xdp_frame *xdp);
+	int			(*ndo_xdp_xmit)(struct net_device *dev, int n,
+						struct xdp_frame **xdp);
 	void			(*ndo_xdp_flush)(struct net_device *dev);
 };
 
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a9cd5c93dd2b..77908311ec98 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -232,24 +232,31 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 		prefetch(xdpf);
 	}
 
-	for (i = 0; i < bq->count; i++) {
-		struct xdp_frame *xdpf = bq->q[i];
-		int err;
-
-		err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
-		if (err) {
-			drops++;
-			xdp_return_frame_rx_napi(xdpf);
-		} else {
-			sent++;
-		}
+	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q);
+	if (sent < 0) {
+		sent = 0;
+		goto error;
 	}
+	drops = bq->count - sent;
+out:
 	bq->count = 0;
 
 	trace_xdp_devmap_xmit(&obj->dtab->map, obj->bit,
 			      sent, drops, bq->dev_rx, dev);
 	bq->dev_rx = NULL;
 	return 0;
+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++) {
+		struct xdp_frame *xdpf = bq->q[i];
+
+		/* RX path under NAPI protection, can return frames faster */
+		xdp_return_frame_rx_napi(xdpf);
+		drops++;
+	}
+	goto out;
 }
 
 /* __dev_map_flush is called from xdp_do_flush_map() which _must_ be signaled
diff --git a/net/core/filter.c b/net/core/filter.c
index 36cf2f87d742..1d75f9322275 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3039,7 +3039,7 @@ static int __bpf_tx_xdp(struct net_device *dev,
 			u32 index)
 {
 	struct xdp_frame *xdpf;
-	int err;
+	int sent;
 
 	if (!dev->netdev_ops->ndo_xdp_xmit) {
 		return -EOPNOTSUPP;
@@ -3049,9 +3049,9 @@ static int __bpf_tx_xdp(struct net_device *dev,
 	if (unlikely(!xdpf))
 		return -EOVERFLOW;
 
-	err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
-	if (err)
-		return err;
+	sent = dev->netdev_ops->ndo_xdp_xmit(dev, 1, &xdpf);
+	if (sent <= 0)
+		return sent;
 	dev->netdev_ops->ndo_xdp_flush(dev);
 	return 0;
 }

[bpf-next V5 PATCH 7/8] xdp/trace: extend tracepoint in devmap with an err

[Jesper Dangaard Brouer]

Extending tracepoint xdp:xdp_devmap_xmit in devmap with an err code
allow people to easier identify the reason behind the ndo_xdp_xmit
call to a given driver is failing.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/trace/events/xdp.h |   10 ++++++----
 kernel/bpf/devmap.c        |    5 +++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index 2e9ef0650144..1ecf4c67fcf7 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -234,9 +234,9 @@ TRACE_EVENT(xdp_devmap_xmit,
 	TP_PROTO(const struct bpf_map *map, u32 map_index,
 		 int sent, int drops,
 		 const struct net_device *from_dev,
-		 const struct net_device *to_dev),
+		 const struct net_device *to_dev, int err),
 
-	TP_ARGS(map, map_index, sent, drops, from_dev, to_dev),
+	TP_ARGS(map, map_index, sent, drops, from_dev, to_dev, err),
 
 	TP_STRUCT__entry(
 		__field(int, map_id)
@@ -246,6 +246,7 @@ TRACE_EVENT(xdp_devmap_xmit,
 		__field(int, sent)
 		__field(int, from_ifindex)
 		__field(int, to_ifindex)
+		__field(int, err)
 	),
 
 	TP_fast_assign(
@@ -256,16 +257,17 @@ TRACE_EVENT(xdp_devmap_xmit,
 		__entry->sent		= sent;
 		__entry->from_ifindex	= from_dev->ifindex;
 		__entry->to_ifindex	= to_dev->ifindex;
+		__entry->err		= err;
 	),
 
 	TP_printk("ndo_xdp_xmit"
 		  " map_id=%d map_index=%d action=%s"
 		  " sent=%d drops=%d"
-		  " from_ifindex=%d to_ifindex=%d",
+		  " from_ifindex=%d to_ifindex=%d err=%d",
 		  __entry->map_id, __entry->map_index,
 		  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
 		  __entry->sent, __entry->drops,
-		  __entry->from_ifindex, __entry->to_ifindex)
+		  __entry->from_ifindex, __entry->to_ifindex, __entry->err)
 );
 
 #endif /* _TRACE_XDP_H */
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 77908311ec98..ae16d0c373ef 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -220,7 +220,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 			 struct xdp_bulk_queue *bq)
 {
 	struct net_device *dev = obj->dev;
-	int sent = 0, drops = 0;
+	int sent = 0, drops = 0, err = 0;
 	int i;
 
 	if (unlikely(!bq->count))
@@ -234,6 +234,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 
 	sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q);
 	if (sent < 0) {
+		err = sent;
 		sent = 0;
 		goto error;
 	}
@@ -242,7 +243,7 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
 	bq->count = 0;
 
 	trace_xdp_devmap_xmit(&obj->dtab->map, obj->bit,
-			      sent, drops, bq->dev_rx, dev);
+			      sent, drops, bq->dev_rx, dev, err);
 	bq->dev_rx = NULL;
 	return 0;
 error:

[bpf-next V5 PATCH 8/8] samples/bpf: xdp_monitor use err code from tracepoint xdp:xdp_devmap_xmit

[Jesper Dangaard Brouer]

Update xdp_monitor to use the recently added err code introduced
in tracepoint xdp:xdp_devmap_xmit, to show if the drop count is
caused by some driver general delivery problem.  Other kind of drops
will likely just be more normal TX space issues.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 samples/bpf/xdp_monitor_kern.c |   10 ++++++++++
 samples/bpf/xdp_monitor_user.c |   35 ++++++++++++++++++++++++++++++-----
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/xdp_monitor_kern.c b/samples/bpf/xdp_monitor_kern.c
index 2854aa0665ea..ad10fe700d7d 100644
--- a/samples/bpf/xdp_monitor_kern.c
+++ b/samples/bpf/xdp_monitor_kern.c
@@ -125,6 +125,7 @@ struct datarec {
 	u64 processed;
 	u64 dropped;
 	u64 info;
+	u64 err;
 };
 #define MAX_CPUS 64
 
@@ -228,6 +229,7 @@ struct devmap_xmit_ctx {
 	int sent;		//	offset:24; size:4; signed:1;
 	int from_ifindex;	//	offset:28; size:4; signed:1;
 	int to_ifindex;		//	offset:32; size:4; signed:1;
+	int err;		//	offset:36; size:4; signed:1;
 };
 
 SEC("tracepoint/xdp/xdp_devmap_xmit")
@@ -245,5 +247,13 @@ int trace_xdp_devmap_xmit(struct devmap_xmit_ctx *ctx)
 	/* Record bulk events, then userspace can calc average bulk size */
 	rec->info += 1;
 
+	/* Record error cases, where no frame were sent */
+	if (ctx->err)
+		rec->err++;
+
+	/* Catch API error of drv ndo_xdp_xmit sent more than count */
+	if (ctx->drops < 0)
+		rec->err++;
+
 	return 1;
 }
diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index 7e18a454924c..dd558cbb2309 100644
--- a/samples/bpf/xdp_monitor_user.c
+++ b/samples/bpf/xdp_monitor_user.c
@@ -117,6 +117,7 @@ struct datarec {
 	__u64 processed;
 	__u64 dropped;
 	__u64 info;
+	__u64 err;
 };
 #define MAX_CPUS 64
 
@@ -152,6 +153,7 @@ static bool map_collect_record(int fd, __u32 key, struct record *rec)
 	__u64 sum_processed = 0;
 	__u64 sum_dropped = 0;
 	__u64 sum_info = 0;
+	__u64 sum_err = 0;
 	int i;
 
 	if ((bpf_map_lookup_elem(fd, &key, values)) != 0) {
@@ -170,10 +172,13 @@ static bool map_collect_record(int fd, __u32 key, struct record *rec)
 		sum_dropped        += values[i].dropped;
 		rec->cpu[i].info = values[i].info;
 		sum_info        += values[i].info;
+		rec->cpu[i].err = values[i].err;
+		sum_err        += values[i].err;
 	}
 	rec->total.processed = sum_processed;
 	rec->total.dropped   = sum_dropped;
 	rec->total.info      = sum_info;
+	rec->total.err       = sum_err;
 	return true;
 }
 
@@ -274,6 +279,18 @@ static double calc_info(struct datarec *r, struct datarec *p, double period)
 	return pps;
 }
 
+static double calc_err(struct datarec *r, struct datarec *p, double period)
+{
+	__u64 packets = 0;
+	double pps = 0;
+
+	if (period > 0) {
+		packets = r->err - p->err;
+		pps = packets / period;
+	}
+	return pps;
+}
+
 static void stats_print(struct stats_record *stats_rec,
 			struct stats_record *stats_prev,
 			bool err_only)
@@ -412,11 +429,12 @@ static void stats_print(struct stats_record *stats_rec,
 
 	/* devmap ndo_xdp_xmit stats */
 	{
-		char *fmt1 = "%-15s %-7d %'-12.0f %'-12.0f %'-10.2f %s\n";
-		char *fmt2 = "%-15s %-7s %'-12.0f %'-12.0f %'-10.2f %s\n";
+		char *fmt1 = "%-15s %-7d %'-12.0f %'-12.0f %'-10.2f %s %s\n";
+		char *fmt2 = "%-15s %-7s %'-12.0f %'-12.0f %'-10.2f %s %s\n";
 		struct record *rec, *prev;
-		double drop, info;
+		double drop, info, err;
 		char *i_str = "";
+		char *err_str = "";
 
 		rec  =  &stats_rec->xdp_devmap_xmit;
 		prev = &stats_prev->xdp_devmap_xmit;
@@ -428,22 +446,29 @@ static void stats_print(struct stats_record *stats_rec,
 			pps  = calc_pps(r, p, t);
 			drop = calc_drop(r, p, t);
 			info = calc_info(r, p, t);
+			err  = calc_err(r, p, t);
 			if (info > 0) {
 				i_str = "bulk-average";
 				info = (pps+drop) / info; /* calc avg bulk */
 			}
+			if (err > 0)
+				err_str = "drv-err";
 			if (pps > 0 || drop > 0)
 				printf(fmt1, "devmap-xmit",
-				       i, pps, drop, info, i_str);
+				       i, pps, drop, info, i_str, err_str);
 		}
 		pps = calc_pps(&rec->total, &prev->total, t);
 		drop = calc_drop(&rec->total, &prev->total, t);
 		info = calc_info(&rec->total, &prev->total, t);
+		err  = calc_err(&rec->total, &prev->total, t);
 		if (info > 0) {
 			i_str = "bulk-average";
 			info = (pps+drop) / info; /* calc avg bulk */
 		}
-		printf(fmt2, "devmap-xmit", "total", pps, drop, info, i_str);
+		if (err > 0)
+			err_str = "drv-err";
+		printf(fmt2, "devmap-xmit", "total", pps, drop,
+		       info, i_str, err_str);
 	}
 
 	printf("\n");

Re: [bpf-next V5 PATCH 0/8] xdp: introduce bulking for ndo_xdp_xmit API

[Alexei Starovoitov]

On Thu, May 24, 2018 at 04:45:41PM +0200, Jesper Dangaard Brouer wrote:
> This patchset change ndo_xdp_xmit API to take a bulk of xdp frames.
> 
> When kernel is compiled with CONFIG_RETPOLINE, every indirect function
> pointer (branch) call hurts performance. For XDP this have a huge
> negative performance impact.
> 
> This patchset reduce the needed (indirect) calls to ndo_xdp_xmit, but
> also prepares for further optimizations.  The DMA APIs use of indirect
> function pointer calls is the primary source the regression.  It is
> left for a followup patchset, to use bulking calls towards the DMA API
> (via the scatter-gatter calls).
> 
> The other advantage of this API change is that drivers can easier
> amortize the cost of any sync/locking scheme, over the bulk of
> packets.  The assumption of the current API is that the driver
> implemementing the NDO will also allocate a dedicated XDP TX queue for
> every CPU in the system.  Which is not always possible or practical to
> configure. E.g. ixgbe cannot load an XDP program on a machine with
> more than 96 CPUs, due to limited hardware TX queues.  E.g. virtio_net
> is hard to configure as it requires manually increasing the
> queues. E.g. tun driver chooses to use a per XDP frame producer lock
> modulo smp_processor_id over avail queues.
> 
> I'm considered adding 'flags' to ndo_xdp_xmit, but it's not part of
> this patchset.  This will be a followup patchset, once we know if this
> will be needed (e.g. for non-map xdp_redirect flush-flag, and if
> AF_XDP chooses to use ndo_xdp_xmit for TX).
> 
> ---
> V5: Fixed up issues spotted by Daniel and John
> 
> V4: Splitout the patches from 4 to 8 patches.  I cannot split the
> driver changes from the NDO change, but I've tried to isolated the NDO
> change together with the driver change as much as possible.

The patch 6/8 would have benefited from a review from Intel folks,
but the series have been pending for too long already, hence
Applied to bpf-next.
Please address any follow up reviews if/when they come.
Thanks Jesper.