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Re: POSIX threads hard to implement in Windows

Cross-posted to 3 groups.

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On 7/7/2011 7:12 PM, MikeP wrote:
> Robert Wessel wrote:
>> On Fri, 08 Jul 2011 08:07:30 +1200, Ian Collins<ian-news@hotmail.com>
>> wrote:
>
>>> Does the windows API support process shared mutexes?  The C1x
>>> proposal doesn't include them probably because the process model is
>>> beyond the C standard.
>>
>>
>> Sure.  Most of the synchronization objects in Windows are system wide.
>
> CAN be. If you name them, THEN they can be used amongst processes.
> Unnamed synch objects are intra-process. Whether having unnamed synch
> objects makes them lighter-weight (higher performance) in usage, I don't
> know. Simple enough to profile though.
>

these mutexes are very expensive, almost absurdly slow. a lock/unlock 
cycle takes around 1-2us, which is far longer than most operations one 
may reasonably want to lock (on a reasonably modern computer, this is 
around 3000 to 6000 clock cycles).

"Critical Sections" are a bit faster, and so are preferable to the 
generic mutex objects (but, much faster than dead slow is still not 
necessarily fast).


much faster IME was to implement a spinlock-with-sleeep operation (using 
"InterlockedExchange", ...), which can generally handle 
locking/unlocking in the low ns range (more around 5ns or so).

the above fast mutexes make a lot more sense when ones' goal is 
something like:
lock mutex;
add entry to cross-thread linked list (such as a message queue);
unlock mutex.

or: the corresponding action to remove something from a linked-list.


rather than... whatever the hell MS intends their mutexes for...

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Thread

POSIX threads hard to implement in Windows (was: C is fixed or not ?) Noob <root@127.0.0.1> - 2011-07-07 15:17 +0200
  Re: POSIX threads hard to implement in Windows William Ahern <william@wilbur.25thandClement.com> - 2011-07-07 11:21 -0700
    Re: POSIX threads hard to implement in Windows Ian Collins <ian-news@hotmail.com> - 2011-07-08 08:07 +1200
      Re: POSIX threads hard to implement in Windows Robert Wessel <robertwessel2@yahoo.com> - 2011-07-07 16:01 -0500
        Re: POSIX threads hard to implement in Windows "MikeP" <mp011011@some.org> - 2011-07-07 21:12 -0500
          Re: POSIX threads hard to implement in Windows Robert Wessel <robertwessel2@yahoo.com> - 2011-07-07 23:33 -0500
            Re: POSIX threads hard to implement in Windows "MikeP" <mp011011@some.org> - 2011-07-07 23:49 -0500
          Re: POSIX threads hard to implement in Windows BGB <cr88192@hotmail.com> - 2011-08-03 07:32 -0700
      Re: POSIX threads hard to implement in Windows William Ahern <william@wilbur.25thandClement.com> - 2011-07-07 15:06 -0700
    Re: POSIX threads hard to implement in Windows lawrence.jones@siemens.com - 2011-07-10 16:08 -0400
      Re: POSIX threads hard to implement in Windows William Ahern <william@wilbur.25thandClement.com> - 2011-07-10 16:09 -0700
        Re: POSIX threads hard to implement in Windows James Kuyper <jameskuyper@verizon.net> - 2011-07-11 06:20 -0400
          Re: POSIX threads hard to implement in Windows Ian Collins <ian-news@hotmail.com> - 2011-07-11 22:36 +1200
      Re: POSIX threads hard to implement in Windows scott@slp53.sl.home (Scott Lurndal) - 2011-07-11 16:18 +0000
        Re: POSIX threads hard to implement in Windows Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2011-07-12 13:30 +0100
  Re: POSIX threads hard to implement in Windows (was: C is fixed or not ?) Joshua Maurice <joshuamaurice@gmail.com> - 2011-07-07 19:01 -0700
  Re: POSIX threads hard to implement in Windows (was: C is fixed or not ?) "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-07-14 23:05 +0200

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