> That's what they said in the nineties as well. Didn't happen so far. > Although there are aspects of NUMA in all processors today, it seems the > general consensus is that you need very specific cases for any affinity > sensitive code to actually be faster. >
Yes, except if OSes put your process into a single group by default, and if you need to manually override affinity for using all cores. Then you have to be NUMA-aware for using 100% of the CPU. > > That said, it's not great the the QThread ideal thread count isn't correct > (assuming it isn't). If you want to investigate this issue and see if you > can come up with a fix that doesn't break everything else... > > You are right in the sense that it's not the purpose of Qt to implement fine-grained affinity. But using a sub-optimal number of cores in QtConcurrent and by taking the return value of idealThreadCount() is not good at all. This means, that idealThreadCount() should be fixed to take into account all cores, at least. Disabling NUMA in the BIOS did change the result of idealThreadCount() from 20 to 40, so yes the result was incorrect. I will post a bug report. Under windows, this is because the function only returns the result from GetSystemInfo()whereas it should the more complex GetLogicalProcessorInformation() > If your system is special hardware, just set the number of threads > manually. > This is not a special hardware : a freshly unboxed standard dual CPU HP workstation. > > Bo Thorsen, > Director, Viking Software. > > -- > Viking Software > Qt and C++ developers for hire > http://www.vikingsoft.eu > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest >
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