cvs commit: src/lib/libthr/thread thr_mutex.c src/lib/libkse/thread thr_mutex.c src/include pthread.h

[Julian Elischer]

Daniel Eischen wrote:
> On Mon, 29 Oct 2007, Kris Kennaway wrote:
> 
>> Daniel Eischen wrote:
>>> On Mon, 29 Oct 2007, Kris Kennaway wrote:
>>>
>>>> Daniel Eischen wrote:
>>>>>
>>>>> The libkse implementation already spins for a bit.  The default
>>>>> number of spins is 500.
>>>>
>>>> OK, cool.
>>>>
>>>>> I'm not sure that another mutex type is warranted, the default
>>>>> mutex implementation should be adaptive I think.
>>>>
>>>> The point being that certain existing applications already know 
>>>> about this mutex name and will use it automatically when it exists.
>>>>
>>>> I am a bit wary of making this the default type though.  The 
>>>> algorithm is a pessimization when the conditions described above are 
>>>> not true.
>>>
>>> I agree, and it applies a little to the KSE approach also.
>>> Spinning is mostly a hack for not being able to tell in
>>> userland if a thread is swapped in/out or is on another
>>> CPU.  If you solve that problem, then you can make the
>>> default mutex adaptive.
>>
>> Yeah.  It looks like Solaris does this.  In principle you could do it 
>> cheaply with a shared page, I'm not sure what Solaris does.
> 
> I think we should add back the thread mailbox for libthr threads.
> I was in favor of keeping the mailbox for libthr, and this might
> be a good use for it.

I have hopes that we can add a per-thread shared page above the stack.
(if asked for)