HEADS UP! 6.0-RELEASE coming

[Scott Long]

Marc Olzheim wrote:
> On Tue, Nov 01, 2005 at 06:33:21PM +0600, Max Khon wrote:
> 
>>Hi!
>>
>>On Tue, Nov 01, 2005 at 12:29:00PM +0100, Marc Olzheim wrote:
>>
>>
>>>>Linking against -lthr (or even -lc_r!) instead of -lpthread solves gdb
>>>>"The program no longer exists." problem for me on RELENG_6.
>>>
>>>Well, yes, but that's not the same. While running on M:N KSE, all sorts
>>>of locking needs to be correct, which with non M:N threading you can get
>>>away with some (intentional or not) sloppiness. So debugging a fully
>>>threaded program with a non M:N threadlib is not always useful.
>>
>>I do not think that maintaining M:N thread lib is feasible, given the lack
>>of resources. Solaris has already moved from M:N to 1:1. Linux (NPTL) is 1:1
>>as well.
> 
> 
> Well, each threading system has it's own application. Having an easy way
> to have one multithreaded process use multiple CPUs is a big win in any
> case. Especially in computationally intensive tasks...
> 
> Marc

There is little difference between 1:1 and M:N from the application's
point of view.  Both will allow multiple application threads to run
concurrently on multiple CPUs, and both will allow other process threads
to run when the current thread blocks in the kernel.  The difference is
in the details with how they are scheduled and what kernel resources
they use.  1:1 has the advantage of being much less complex to implement
and maintain, while M:N has the theoretical advantage of cheaper thread
context switches.  That theory hasn't panned out, though, due to
synchronization requirements and the technical requirements of proper
TLS support.

Scott