netdev - Re: [PATCH net-next] openvswitch: include datapath actions with sampled-packet upcall to userspace

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Date:	Wed, 27 May 2015 22:57:04 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Jesse Gross <jesse@...ira.com>
Cc:	Neil McKee <neil.mckee@...on.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] openvswitch: include datapath actions with
 sampled-packet upcall to userspace

On Wed, May 27, 2015 at 9:16 PM, Jesse Gross <jesse@...ira.com> wrote:
> On Wed, May 27, 2015 at 7:46 PM, Pravin Shelar <pshelar@...ira.com> wrote:
>> On Wed, May 27, 2015 at 2:10 PM, Jesse Gross <jesse@...ira.com> wrote:
>>> On Fri, May 22, 2015 at 10:53 AM, Pravin Shelar <pshelar@...ira.com> wrote:
>>>> On Wed, May 20, 2015 at 12:32 PM, Neil McKee <neil.mckee@...on.com> wrote:
>>>>> diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
>>>>> index b491c1c..ee5760d 100644
>>>>> --- a/net/openvswitch/actions.c
>>>>> +++ b/net/openvswitch/actions.c
>>>>> @@ -608,7 +608,8 @@ static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port)
>>>>>  }
>>>>>
>>>>>  static int output_userspace(struct datapath *dp, struct sk_buff *skb,
>>>>> -                           struct sw_flow_key *key, const struct nlattr *attr)
>>>>> +                           struct sw_flow_key *key, const struct nlattr *attr,
>>>>> +                           const struct nlattr *actions, int actions_len)
>>>>>  {
>>>>>         struct ovs_tunnel_info info;
>>>>>         struct dp_upcall_info upcall;
>>>>> @@ -619,6 +620,8 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb,
>>>>>         upcall.userdata = NULL;
>>>>>         upcall.portid = 0;
>>>>>         upcall.egress_tun_info = NULL;
>>>>> +       upcall.actions = actions;
>>>>> +       upcall.actions_len = actions_len;
>>>>>
>>>> Rather than unconditionally passing actions to the upcall, there
>>>> should be attribute in ovs_userspace_attr to request the actions list.
>>>
>>> Why? It seems simpler to just always pass the actions and I'm not sure
>>> that this is really performance critical (which is the only reason
>>> that comes to mind to not always pass this).
>>
>> This is only required for sFlow sampling so I do not think we should
>> send it on every upcall.
>
> But what is the downside?

This increases memory allocation in atomic context but if you think
this makes code complicated then I am fine without the attribute.
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