xdp: change ndo_xdp_xmit API to support bulking
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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 44d4f3d..d3dcfcb 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;
- }
-out:
+ 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);
+
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)