On 2018/11/8 18:17, Peter Zijlstra wrote: > On Thu, Nov 08, 2018 at 07:32:46AM +0100, Ingo Molnar wrote: >> >> * Aubrey Li <aubrey...@intel.com> wrote: >> >>> Expose the per-task cpu specific thread state value, it's helpful >>> for userland to classify and schedule the tasks by different policies >> >> That's pretty vague - what exactly would use this information? I'm sure >> you have a usecase in mind - could you please describe it? > > Yeah, "thread_state" is a pretty terrible name for this.
task_struct has a CPU specific element "thread", I quote it to here to create a generic interface to expose CPU specific state of the task. Like /proc/<pid>/stat, I plan to use this "thread_state" to host any CPU specific state, including AVX state(now only), and any other states(may come soon). So this interface may be extended in future like the following: #cat /proc/<pid>/thread_state 1 0 0 > The use-case is > detectoring which tasks use AVX3 such that a userspace component (think > job scheduler) can cluster them together.> > The 'problem' is that running AVX2+ code drops the max clock, because > you light up the massive wide (and thus large area) paths. Thanks to explain this. > > So maybe something like "simd_active" is a better name, dunno. As above, maybe the name can be hidden by thread_state? > > Or maybe "simd_class" and we can write out 0,1,2,3 depending on the AVX > class being used, dunno. It might make sense to look at what other arch > SIMD stuff looks like to form this interface. > A task may use 1,2,3 simultaneously, as a scheduler hint, it's just cluster or not, so 0/1 may be good enough. Thanks, -Aubrey
