[Click] Threading and locks

[Eddie Kohler]

1. What they said is all true.

2. In addition, handler code can execute concurrently with Click packet 
processing tasks on an SMP machine.

Eddie


On Sep 11, 2004, at 6:04 PM, Nikitas Liogkas wrote:

> Basically everything will run on one thread, even with SMP enabled, 
> unless:
> 1. you use "--threads=2" (or however many processors you have) when 
> running
> click-install, AND
>
> 2. you include a StaticThreadSched/BalancedThreadSched in your
> configuration; these will assign tasks to run on different processors: 
> the
> former sets a static assignment, while the latter moves tasks at 
> runtime
> from one processor to the other as needed to maintain a reasonable 
> load on
> each processor. If you don't include any of these elements in your
> configuration, there will be 2 threads, but nothing will ever be run 
> on the
> second one, since all tasks are by default assigned to the first 
> thread.
>
> Hope this helps...
>
> nikitas
>
>
> ----- Original Message -----
> From: "Giovanni Tusa" <gtusa at diit.unict.it>
> To: <click at amsterdam.lcs.mit.edu>; <kevin_mitchell at agilent.com>
> Sent: Monday, September 06, 2004 2:18 AM
> Subject: Re: [Click] Threading and locks
>
>
>>
>> ----- Original Message -----
>> From: <kevin_mitchell at agilent.com>
>> To: <click at amsterdam.lcs.mit.edu>
>> Sent: Monday, September 06, 2004 10:45 AM
>> Subject: [Click] Threading and locks
>>
>>
>>> I have a simple question about threading.  I've written some Click
>> elements that are used in a script that is processing packets from two
>> interfaces, and the elements also use timers.  Multiple elements
> manipulate
>> a shared data structure.  All this is running in kernel mode.  Is 
>> Click
>> single-threaded, even in an SMP environment, so I don't need to worry
> about
>> adding locks etc when accessing the shared structures.  Or are 
>> multiple
>> threads potentially in use, and so I should assume the code in 
>> multiple
>> elements could be running simultaneously, and therefore I need to use
>> locking?  I noticed the docs talk about tasks potentially running on
>> multiple threads, but I wasn't sure what the implications were for
>> packet-processing and timers.
>>>
>>> Kevin
>>>
>>
>> According to my knowledge in the use of SMP Click in a multiprocessor
>> hardware architecture, multiple threads activation is not automatic, 
>> also
> in
>> an SMP environment.
>> For example, in a dual processor system, the ""--enable-multithread=2"
>> option must be added during Click configuration. In addition, to make 
>> the
>> use of multiple threads
>> effective, the StaticThreadSched element, or the BalancedThreadSched 
>> (the
>> old SortedTaskSched) element, in order to activate the Static or the
>> Adaptive CPU scheduling,
>> must be added in the Click configuration script.
>>
>> I hope this information can be helpful for you.
>>
>> Giovanni
>> _______________________________________________
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>>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>>>
>>
>>
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