On Wed, 5 Sep 2018 at 10:50, Srikar Dronamraju <sri...@linux.vnet.ibm.com> wrote: > > * Vincent Guittot <vincent.guit...@linaro.org> [2018-09-05 09:36:42]: > > > > > > > I dont know of any systems that have come with single threaded and > > > multithreaded. However some user can still offline few threads in a core > > > while leaving other cores untouched. I dont really know why somebody > > > would want to do it. For example, some customer was toying with SMT 3 > > > mode in a SMT 8 power8 box. > > > > In this case, it means that we have the same core capacity whatever > > the number of CPUs > > and a core with SMT 3 will be set with the same compute capacity as > > the core with SMT 8. > > Does it still make sense ? > > > > To me it make sense atleast from a power 8 perspective, because SMT 1 > > SMT 2 > SMT 4 > SMT8. So if one core is configured for SMT 2 and other > core is configured for SMT4; all threads being busy, the individual > threads running on SMT2 core will complete more work than SMT 4 core > threads.
I agree for individual thread capacity but at core group level, the core SMT 1 will have the same capacity as core group SMT 8 so load balance will try to balance evenly the tasks between the 2 cores whereas core SMT 8 > core SMT1 , isn't it ? > > -- > Thanks and Regards > Srikar Dronamraju >