[M3devel] ease of switching between pthreads and userthreads?

[Tony Hosking]

On Apr 28, 2011, at 3:29 AM, Olaf Wagner wrote:

> Quoting Tony Hosking <hosking at cs.purdue.edu>:
> 
>> On Apr 27, 2011, at 3:05 AM, Jay K wrote:
>> 
>>> About inlining LOCK I was more echoing your past sentiment
>>> than giving my own, and I provided a mitigation:
>>> a) specifically the suggestion that the switchability be an option;
>>>  it'd probably be on by default but people that want to squeeze
>>>  out the extra performance could enable the inlining
>>>  and lose the switchability
>> 
>> It is expected that LOCK will be implemented using CAS (and  equivalents) in the very near future.  I have a student working on  it.  This will be incompatible with the current user-threads  implementation of LOCK.  It will be too painful to support both  using a compiler switch.
> 
> Couldn't we change the existing user threads to use CAS for locks, too,
> in order to gain runtime switching of thread implementations?
> I have neither thought much about it nor looked at the implementation
> in recent years, so I hope it's no stupid question.

Hmm. Yes, I suppose we could.  It might degrade performance of the user-level (uniprocessor) threads implementation.

> 
> Olaf
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