[Click] Bug in QuickNoteQueue

[Ashish Sharma]

Hi Eddie,

Thanks for your effort in checking in this new element. I got a chance
to test it out only now. There is however one bug in this, the
empty_note.sleep is only called when the queue becomes empty, but if
the queue is empty to begin with, this goes into a constant polling
mode, calling pull in a loop. Here is a possible patch that fixes it.
Please consider applying the following patch. Also the suggestion of
making the SLEEPINESS_TRIGGER value configurable seems like a good
idea. I can write a patch if you think it should be done.

diff --git a/elements/standard/quicknotequeue.cc
b/elements/standard/quicknotequeue.cc
index 88d8b3a..4350346 100644
--- a/elements/standard/quicknotequeue.cc
+++ b/elements/standard/quicknotequeue.cc
@@ -46,7 +46,10 @@ QuickNoteQueue::pull(int)
     if (h != t)
        return pull_success(h, t, nh);
     else
+    {
+       _empty_note.sleep();
        return 0;
+    }
 }

 CLICK_ENDDECLS


Thanks
Ashish


SUB: Notifier::upstream_empty_signal is always active

On Sun, Jun 14, 2009 at 9:47 AM, Eddie Kohler<kohler at cs.ucla.edu> wrote:
>>  If you want not even one failed pull(), that will take some
>> reorganization of the code to clear the notifier in a different place (this
>> would be easy to do).
>
>
> You may be interested in QuickNoteQueue, just checked in.
>
> Eddie
>
>
>
>>
>>> Since the valid/invalid test is an expensive
>>> one, what I would like is for the Notifier signal to act like a test
>>> function, so I only perform the valid/invalid operation if a queue is
>>> non-empty. Further, in case the queue is not empty but belongs to the set
>>> of
>>> "invalid" queues, I do not want to put the packet back at the head of the
>>> queue (of which I cannot think of a simple way of doing from within the
>>> scheduler element).
>>
>> More generally, it seems like you should make your valid/invalid check
>> cheaper.  There are many possible ways to do this, including caching old
>> values of the check and only updating the cache when necessary.
>>
>> Eddie
>>
>>
>>> One solution is that I extend the Queue element to include a test
>>> function
>>> and along with the signal check the test function.
>>>
>>> Is there a clean way to make the Notifier signal active only when the
>>> input
>>> queue is really non-empty and not a false alarm?
>>>
>>> Thank you for your time. I would really appreciate any suggestions or
>>> thoughts.
>>>
>>> Thanks
>>> Ashish
>>> _______________________________________________
>>> click mailing list
>>> click at amsterdam.lcs.mit.edu
>>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>>
>> _______________________________________________
>> click mailing list
>> click at amsterdam.lcs.mit.edu
>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>