[Click] Question around RouterThread

[Eddie Kohler]

Hi Beyers,

On 5/17/11 2:14 PM, Beyers Cronje wrote:
> Hi,
>
> I've been toying with multithreading in click, specifically in userlevel
> click. My understanding is that all click threads participate in running
> timers and os (selected etc).

Yes, that's right.

> I'm thinking about testing something where a
> user can specify that certain threads should not participate in any timers
> or selected processing and only process task(s) allocated to it. As a simple
> example consider the following userlevel config:
>
> fd::FromDevice(eth0) ->  Classifier(*some pattern*) ->  Queue ->
> td::ToDump(/dev/null);
> StaticThreadSched(fd 0, td 1);
>
>
> If FromDevice or whatever source element processes a constant high packet
> rate, and ToDump only a fraction of packets as filtered by Classifier it
> would make sense to have fd dedicate to processing RX packets and have the
> td thread handle all other non-task related processes. Throw in a
> ControlSocket and maybe a couple more dumps I'm pretty sure it will affect
> fd performance.
>
> So my question, do you guys feel this will make any difference? Is my
> understanding on how RouterThread handles timers etc wrong? I'm really
> curious to hear your thoughts on this.

I think this is a potentially interesting direction to move.  Eventually, 
though, I want this to move in a different direction, in which selected file 
descriptors, timers, and even handlers are handled by threads *the same way as 
tasks*.  That is, if StaticThreadSched(td 1) is given, then td's 
Timer/selected/etc. will be handled by thread 1.  This would simplify 
reasoning about multithreading interactions.  Currently we have, for example, 
selected() operations and timers that emit packets -- but that can cause 
problems if the timer runs on a different thread from the associated task.

Make sense?

Eddie


>
> Beyers
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