Re: kernel thread as real threads..

Julian Elischer wrote:
> 

>>> However I would like to suggest that we change the way that aio works..
>>>
>>> My suggestion is that when a process does AIO, that we "fork a 
>>> ksegroup" and attach it to the
>>> process, and assign it a (or some) worker thread to do the aio work.  
>>> The userland process would
>>> be oblivious of the extra (kernel) threads in that kseg and they 
>>> would be independently schedulable.
>>> They would however automatically have full access to the correct 
>>> address space.
>>>
>> These threads should be invisible to userland debugger, and other code
>> current unknown, for example, signal code ? The idea seems simply but we
>> may in fact encounter problem, because you inject unknown threads to a
> 
> 
>> process. :-)
> 
> 
> If the userland doesn't know about them, how would it affect it?
I said it should be invisible to userland debugger, but ptrace interface
will expose it to userland, you have to calculate actually threads
number for PT_GETNUMLWPS, you also have to filter aio threads out for
PT_GETLWPLIST, you also have to figure out first threads which is 
meanful to userland for PT_LWPINFO, others I don't know yet.
I didn't say that injecting unknown threads into process is not 
practical, but it should be carefully to not break current stable code.

> As a kernel thread it wouldn't take part in signals, other than to abort 
> when the process exits.
Also, process suspension should suspend these aio threads.

> it    WOULD accumulate cpu time for the process.. but that is just fair. 
> currently I think that
> aio is "free".
> 
Yes, you are right.

> Anyhow I'm not ready to try do it now.. As the current patches leave the 
> status-quo for aio.
> 
> 
OK.
> 
> 
> 
> 
> 
>> I still prefer current model, also the aiod threads can be reused for 
>> multiple
>> processes.
> 
> 
> that is both a positive and a negative when it comes to accounting.
> 
> 
>