Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx> writes:
> 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.
>
>> So why not just fix that instead?
>
> The queues are shared with packets from stack sent from peer. That's
> because I needed the lock. I have tried to separate the queues, one for
> redirect and one for stack, but receiver side got too complicated and it
> ended up with worse performance.
I meant fix it with configuration. Now many receive queues are you
running on the veth device in your benchmarks, and how have you
configured the RPS?
-Toke
