[Click] Queues and notifications

[Eddie Kohler]

Some answers:

> I am trying to understand the behavior of signals. When a Notifier
> sets its signal, shouldn't it set the signal of all listeners
> registered with it? (ie is a derived signal the OR of all the base
> signal of pull elements that are downsteam of the notifier?)

Close, but a bit backwards.  Listeners don't have signals of their own, 
Notifiers do.  (I.e., Queues have their own signals, and downstream 
ToDevices derive signals from the upstream Queues.)  The signal returned 
by Notifier::upstream_empty_signal is derived from signals that belong 
to all the upstream Notifiers; basically, it's the "or".

Eddie


> 
> 
> Below is another simple config that triggers the problem. The counters
> show that no packets ever leave q1 and reach ToDevice.
> 
> cheers,
> 
> geoffrey
> 
> 
> 
> InfiniteSource(DATA \<00 00 c0 ae 67 ef  00 00 00 00 00 00  08 00
> 45 00 00 28  00 00 00 00  40 11 77 c3  01 00 00 01
> 02 00 00 02  13 69 13 69  00 14 d6 41  55 44 50 20
> 70 61 63 6b  65 74 21 0a>, LIMIT 10, STOP false)
>     -> Strip(14)
>     -> CheckIPHeader()
>     -> q0 :: Queue
>     -> DelayUnqueue(1)
>     -> c0 :: Counter
>     -> q1 :: Queue
>     -> DelayShaper(1)
>     -> Unstrip(14)
>     -> c1 :: Counter
>     -> ToDevice(eth0);
> 
> 
> 
> On 1/25/07, Mike Wilson <mlw2 at arl.wustl.edu> wrote:
>> I've got a large, complex click config where I read from UDP sockets and
>> write to a raw socket, routing packets from UDP tunnels.  Unfortunately, I
>> can't seem to get notifications working in the Queues.
>>
>> I've stripped the config down to a fairly simple case that replicates the
>> problem, at least on my system.  If I use Queue or NotifierQueue
>> components for the queues, I either get nothing out the interface, or I
>> get 1-2 packets and then nothing.  If I use a SimpleQueue, everything
>> works just fine.
>>
>> My limited understanding is that the SimpleQueue doesn't do notifiers, so
>> the pull components downstream must use polling.  In other words, it's a
>> massive CPU hog - I get 99% utilization to click with a SimpleQueue.  With
>> Queue, I don't even see click in my top(1) list.
>>
>> Am I mis-using the queue components somehow, or is this a bug?  Do
>> RawSockets use notifiers?
>>
>> -Mike Wilson
>>
>> ---replication example---
>>
>> // Warning, this config will send bogus UDP packets to 172.16.46.20.
>> // Unfortunately, the problem doesn't manifest with a Discard at the end.
>>
>> AddressInfo(myip  128.252.160.209,
>>              NetRtr 172.16.46.12,
>>              HostRtr 172.16.46.20,
>>              NetRoute 172.16.46.0/24);
>>
>> PortInfo(NetTun 0xA121,
>>           HostTun 0xA122);
>>
>> out :: RawSocket("UDP");
>> rt :: RangeIPLookup(NetRoute  0, HostRtr 1);
>> sched :: DRRSched();
>>
>> TimedSource -> UDPIPEncap(HostRtr, 5005, HostRtr, 5005) ->
>> IPPrint("Injecting Packet") -> check :: CheckIPHeader;
>> Idle -> rt;
>>
>> check[1] -> Print("Injected Bad packet") -> Discard;
>> check[0] -> IPPrint("Injected Valid Packet") -> GetIPAddress(16) -> rt;
>>
>> rt[0] -> UDPIPEncap(myip, NetTun, NetRtr, NetTun) -> IPPrint("Net Route")
>> -> SimpleQueue -> [0]sched;
>> rt[1] -> UDPIPEncap(myip, HostTun, HostRtr, HostTun) -> IPPrint("Host
>> Route") -> SimpleQueue -> [1]sched;
>>
>> sched -> IPPrint("Sending") -> out;
>>
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>>
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