On 2019/5/23 下午9:51, Toshiaki Makita wrote:
On 19/05/23 (木) 22:29:27, Jesper Dangaard Brouer wrote:
On Thu, 23 May 2019 20:35:50 +0900
Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx> wrote:
On 2019/05/23 20:25, Toke Høiland-Jørgensen wrote:
Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx> writes:
This improves XDP_TX performance by about 8%.
Here are single core XDP_TX test results. CPU consumptions are taken
from "perf report --no-child".
- Before:
7.26 Mpps
_raw_spin_lock 7.83%
veth_xdp_xmit 12.23%
- After:
7.84 Mpps
_raw_spin_lock 1.17%
veth_xdp_xmit 6.45%
Signed-off-by: Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx>
---
drivers/net/veth.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 52110e5..4edc75f 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -442,6 +442,23 @@ static int veth_xdp_xmit(struct net_device
*dev, int n,
return ret;
}
+static void veth_xdp_flush_bq(struct net_device *dev)
+{
+ struct xdp_tx_bulk_queue *bq = this_cpu_ptr(&xdp_tx_bq);
+ int sent, i, err = 0;
+
+ sent = veth_xdp_xmit(dev, bq->count, bq->q, 0);
Wait, veth_xdp_xmit() is just putting frames on a pointer ring. So
you're introducing an additional per-cpu bulk queue, only to avoid
lock
contention around the existing pointer ring. But the pointer ring is
per-rq, so if you have lock contention, this means you must have
multiple CPUs servicing the same rq, no?
Yes, it's possible. Not recommended though.
I think the general per-cpu TX bulk queue is overkill. There is a loop
over packets in veth_xdp_rcv(struct veth_rq *rq, budget, *status), and
the caller veth_poll() will call veth_xdp_flush(rq->dev).
Why can't you store this "temp" bulk array in struct veth_rq ?
Of course I can. But I thought tun has the same problem and we can
decrease memory footprint by sharing the same storage between devices.
For TUN and for its fast path where vhost passes a bulk of XDP frames
(through msg_control) to us, we probably just need a temporary bulk
array in tun_xdp_one() instead of a global one. I can post patch or
maybe you if you're interested in this.
Thanks
Or if other devices want to reduce queues so that we can use XDP on
many-cpu servers and introduce locks, we can use this storage for that
case as well.
Still do you prefer veth-specific solution?
You could even alloc/create it on the stack of veth_poll() and send it
along via a pointer to veth_xdp_rcv).
Toshiaki Makita
