[bpf-next V4 PATCH 2/8] bpf: devmap prepare xdp frames for bulking

Jesper Dangaard Brouer
2018-05-18T13:34:43Z

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.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
kernel/bpf/devmap.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 73 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 808808bf2bf2..cab72c100bb5 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -54,11 +54,18 @@
#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;
+};
+
/* objects in the map */
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;
};

@@ -209,6 +216,38 @@ 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)
+{
+ unsigned int processed = 0, drops = 0;
+ 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) {
+ drops++;
+ xdp_return_frame(xdpf);
+ }
+ processed++;
+ }
+ 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
@@ -224,6 +263,7 @@ 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
@@ -233,6 +273,9 @@ 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);
@@ -255,6 +298,20 @@ 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;
@@ -268,8 +325,7 @@ 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 */
- err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
+ err = bq_enqueue(dst, xdpf);
if (err)
return err;

@@ -288,13 +344,18 @@ 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);
}
}
@@ -306,6 +367,7 @@ 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);
}
@@ -338,6 +400,7 @@ 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;
@@ -352,11 +415,17 @@ 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) {
kfree(dev);