Re: Comments on the KSE option

Robert Watson wrote:
> 
> On Sun, 29 Oct 2006, Lucas James wrote:
> 
>> I read what Paul said was that system scope threads have a different 
>> "fairness" than processes. ie:
>>
>> If your application requires 1000 threads of execution, you can write 
>> it three ways, with 1000 processes, 1000 system scope threads or 1000 
>> process scope threads (or a mix of the three).
>>
>> This whole "fairness" argument is about making system scope threads 
>> have the same priority as process scope threads.  It leaves out the 
>> process model.
>>
>> The real question here is: are we going to make system scope thread 
>> model fair compared to process scope threaded model, or fair compared 
>> to the separate processes model?
>>
>> Yes, the process scope threads are allways going to be the poor man 
>> with regard to priority, but as the kernel doesn't see the threads you 
>> can't do much about it.
> 
> I think there are at least two core questions being discussed here:
> 
> (1) Does the "fairness" model currently implemented in the KSE code mean 
> well,
>     but cause significant performance problems in practice for real-world
>     applications?
> 
> (2) Are the cost and complexity impacts of KSE in kernel architecture
>     outweighed by the flexibility and performance benefits of M:N 
> threading?
> 
> Now is definitely the time for us to be discussing, measuring, 
> experimenting, etc, because addressing the issues of higher concurrency 
> for 7.0 will depend on having decided on a strategy for our scheduler.
> 

I'd like to add

(3) Who is committed to maintaining and improving the M:N and KSE 
architectures for the long term?  THR and 1:1 has an active and 
committed maintainer right now, KSE does not.  Whether KSE is 'better'
is purely academic if no one is willing to actually make it work.

Scott