Sujan said he uses threads to generate files, so there's some chance that his task'll be IO-bound and extra threads will actually increase overall performance.
But this is just a guess and running 21 threads on an 8-core CPU is probably an overkill (unless the task is *really* IO-limited). On Oct 4, 2012 5:52 PM, "Thiago Macieira" <thiago.macie...@intel.com> wrote: > On quinta-feira, 4 de outubro de 2012 15.46.57, André Somers wrote: > > If you think that running 21 threads on an 8 core system will run make > > your task go faster, then Thiago is right: you don't understand your > > problem. > > If you run 8 threads on an 8-core system and they use the CPU fully, then > you're running as fast as you can. > > If you have more threads than the number of processors and if all threads > are > ready to be executed, then the OS will schedule timeslices to each thread. > That means threads get executed and suspended all the time, sometimes > migrating between processors. That adds overhead. > > If it adds overhead, it's slower. Depending on your OS, it might be > considerably slower. > > If you do not understand what I said, understand this: there's a reason why > QtConcurrent runs as many threads as there are processors. > -- > Thiago Macieira - thiago.macieira (AT) intel.com > Software Architect - Intel Open Source Technology Center > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest > >
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