Re: DragonFlyBSD threading model

[Erik Wikström <erik-wikstrom@xxxxxxxxx>]

On 2005-08-01 17:14, Matthew Dillon wrote:
> :Hi,
> :
> :I have been reading up about how the different BSD systems are
> :handling SMP and threading. I gather NetBSD uses scheduler
> :activations, where userland programs are given virtual CPUs which then
> :get mapped to kernel threads for execution (please correct me if my
> :analysis is wrong). FreeBSD appears to use a variant of this idea
> :called KSEs. I believe this is known as M:N.
> :
> :I am not however sure exactly how DragonFlyBSD threads work - each CPU
> :has an LWKT scheduler, and that above this layer there is also a
> :userland scheduler (partially equivalent to the functionality provided
> :by sched_4bsd.c under FreeBSD?) - but my question is how that relates
> :to userland programs - when they have threads..does each program
> :thread map directly to one of the LWKT schedulers on one of the CPUs?
> :Does that make it 1:1?
> :
> :I apologise if this seems like an extremly novide question, this stuff
> :is all very new to me.
> :
> :Thanks in advance, Alex J Burke.
>
>     Basically everything gets mapped onto a LWKT (Light Weight Kernel Thread),
>     including userland processes.
>
>     The LWKT scheduler is a fixed priority scheduler.  For example, if you 
>     do a 'ps ax' you will see a ton of kernel threads in addition to userland,
>     including threads for handling interrupts.  Priorities work something
>     like this:

I've been wondering for some time how the number of LWKT are determined?
Are they created when needed (on interrupts etc) or are there a fixed
amount?

--
Erik Wikström