Windows multi-threading performance issues on multi-core systems

Sean Kelly sean at invisibleduck.org
Tue Dec 15 08:15:04 PST 2009


Steven Schveighoffer Wrote:
> 
> I would suspect something else.  I would expect actually that in an  
> allocation-heavy design, running on multiple cores should be at *least* as  
> fast as running on a single core.  He also only has 2 cores.  For  
> splitting the parallel tasks to 2 cores to take 10x longer is very  
> alarming.  I would suspect application design before the GC in this case.   
> If it's a fundamental D issue, then we need to fix it ASAP, especially  
> since D2 is supposed to be (among other things) an upgrade for multi-core.

Assuming he's right, the only thing I can come up with that makes even the remotest sense is that SuspendThread is ridiculously slow for threads on other cores, but effectively a no-op for threads on the same core.  But the Boehm GC works the same way as far as I know, and if it had such problems I'm sure we'd have heard about it.  It also doesn't seem reasonable that the Windows kernel team would be able to keep something so broken in place.



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