Thu, Oct 12, 2017 at 11:45:43PM CEST, dan...@iogearbox.net wrote:
>On 10/12/2017 07:17 PM, Jiri Pirko wrote:
>> From: Jiri Pirko <j...@mellanox.com>
>>
>> In sch_handle_egress and sch_handle_ingress, don't use tp->q and use
>> dev->ingress_queue which stores the same pointer instead.
>>
>> Signed-off-by: Jiri Pirko <j...@mellanox.com>
>> ---
>> net/core/dev.c | 21 +++++++++++++++------
>> 1 file changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index fcddccb..cb9e5e5 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -3273,14 +3273,18 @@ EXPORT_SYMBOL(dev_loopback_xmit);
>> static struct sk_buff *
>> sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
>> {
>> + struct netdev_queue *netdev_queue =
>> + rcu_dereference_bh(dev->ingress_queue);
>> struct tcf_proto *cl = rcu_dereference_bh(dev->egress_cl_list);
>> struct tcf_result cl_res;
>> + struct Qdisc *q;
>>
>> - if (!cl)
>> + if (!cl || !netdev_queue)
>> return skb;
>> + q = netdev_queue->qdisc;
>
>NAK, no additional overhead in the software fast-path of
>sch_handle_{ingress,egress}() like this. There are users out there
>that use tc in software only, so performance is critical here.
Okay, how else do you suggest I can avoid the need to use tp->q?
I was thinking about storing q directly to net_device, which would safe
one dereference, resulting in the same amount as current cl->q.
Thanks.
