Date: Thu, 10 Apr 2014 11:18:21 -0400 From: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> To: freebsd-net@freebsd.org Subject: Re: Preventing ng_callout() timeouts to trigger packet queuing Message-ID: <5346B63D.4080707@gmail.com> In-Reply-To: <CAJ-VmomsK%2BOYdFCzedSaVCCzvu97zUthbNhYFivgAK8eN5Tnvg@mail.gmail.com> References: <53459C96.5040304@gmail.com> <5345BAE7.4010501@gmail.com> <CAJ-VmomsK%2BOYdFCzedSaVCCzvu97zUthbNhYFivgAK8eN5Tnvg@mail.gmail.com>
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Hi,
By the way this change has opened the gates to greater performance for
us when using ng_callout() inside nodes. In some cases we see twice as
much pps since packets are direct dispatched instead of being queued in
software interrupts threads (swi*).
Thanks,
Karim
PS: I did file a PR : kern/188421
On 09/04/2014 9:09 PM, Adrian Chadd wrote:
> Hi!
>
> Would you mind filing a PR for this?
>
> www.freebsd.org/send-pr.html
>
> That way it won't (hopefully!) get lost.
>
> Thanks!
>
>
> -a
>
>
> On 9 April 2014 14:25, Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> wrote:
>> Hi,
>>
>> Below is a revised patch for this issue. It accounts for nodes or hooks that
>> explicitly need to be queuing:
>>
>> @@ -3632,7 +3632,12 @@ ng_callout(struct callout *c, node_p node, hook_p
>> hook, int ticks,
>>
>> if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
>> return (ENOMEM);
>>
>> - item->el_flags |= NGQF_WRITER;
>> + if ((node->nd_flags & NGF_FORCE_WRITER) ||
>> + (hook && (hook->hk_flags & HK_FORCE_WRITER)))
>>
>> + item->el_flags |= NGQF_WRITER;
>> + else
>>
>> + item->el_flags |= NGQF_READER;
>> +
>> NG_NODE_REF(node); /* and one for the item */
>> NGI_SET_NODE(item, node);
>> if (hook) {
>>
>> Regards,
>>
>> Karim.
>>
>>
>> On 09/04/2014 3:16 PM, Karim Fodil-Lemelin wrote:
>>> Hi List,
>>>
>>> I'm calling out to the general wisdom ... I have seen an issue in netgraph
>>> where, if called, a callout routine registered by ng_callout() will trigger
>>> packet queuing inside the worklist of netgraph since ng_callout() makes my
>>> node suddenly a WRITER node (therefore non reentrant) for the duration of
>>> the call.
>>>
>>> So as soon as the callout function returns, all following packets will get
>>> directly passed to the node again and when the ngintr thread gets executed
>>> then only then will I get the queued packets. This introduces out of order
>>> packets in the flow. I am using the current patch below to solve the issue
>>> and I am wondering if there is anything wrong with it (and maybe contribute
>>> back :):
>>>
>>>
>>> @@ -3632,7 +3632,7 @@ ng_callout(struct callout *c, node_p node, hook_p
>>> hook, int ticks,
>>> if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
>>> return (ENOMEM);
>>>
>>> - item->el_flags |= NGQF_WRITER;
>>> + item->el_flags = NGQF_READER;
>>> NG_NODE_REF(node); /* and one for the item */
>>> NGI_SET_NODE(item, node);
>>> if (hook) {
>>>
>>>
>>> Best regards,
>>>
>>> Karim.
>>> _______________________________________________
>>> freebsd-net@freebsd.org mailing list
>>> http://lists.freebsd.org/mailman/listinfo/freebsd-net
>>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"
>>
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