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

[Daniel Eischen]

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.

-- 
DE