cvs commit: src/lib/libthr/thread thr_mutex.c
src/lib/libkse/thread thr_mutex.c src/include pthread.h
deischen at freebsd.org
Mon Oct 29 14:58:55 PDT 2007
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.
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