Messages in this thread | | | Date | Thu, 26 Sep 2013 11:06:36 -0700 | From | Arjan van de Ven <> | Subject | Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management |
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>>>> >>> >>> Arjan, are you referring to the fact that Intel/SNB systems can exploit >>> memory self-refresh only when the entire system goes idle? Is that why >>> this >>> patchset won't turn out to be that useful on those platforms? >> >> no we can use other things (CKE and co) all the time. >> > > Ah, ok.. > >> just that we found that statistical grouping gave 95%+ of the benefit, >> without the cost of being aggressive on going to a 100.00% grouping >> > > And how do you do that statistical grouping? Don't you need patches similar > to those in this patchset? Or are you saying that the existing vanilla > kernel itself does statistical grouping somehow?
so the way I scanned your patchset.. half of it is about grouping, the other half (roughly) is about moving stuff.
the grouping makes total sense to me. actively moving is the part that I am very worried about; that part burns power to do (and performance).... for which the ROI is somewhat unclear to me (but... data speaks. I can easily be convinced with data that proves one way or the other)
is moving stuff around the 95%-of-the-work-for-the-last-5%-of-the-theoretical-gain or is statistical grouping enough to get > 95% of the gain... without the cost of moving.
> > Also, I didn't fully understand how NUMA policy will help in this case.. > If you want to group memory allocations/references into fewer memory regions > _within_ a node, will NUMA policy really help? For example, in this patchset, > everything (all the allocation/reference shaping) is done _within_ the > NUMA boundary, assuming that the memory regions are subsets of a NUMA node. > > Regards, > Srivatsa S. Bhat >
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