Messages in this thread | | | Date | Wed, 11 Oct 2023 11:02:13 +0800 | Subject | Re: [PATCH -next 1/7] mm_types: add _last_cpupid into folio | From | Kefeng Wang <> |
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On 2023/10/10 20:33, Matthew Wilcox wrote: > On Tue, Oct 10, 2023 at 02:45:38PM +0800, Kefeng Wang wrote: >> At present, only arc/sparc/m68k define WANT_PAGE_VIRTUAL, both of >> them don't support numa balancing, and the page struct is aligned >> to _struct_page_alignment, it is safe to move _last_cpupid before >> 'virtual' in page, meanwhile, add it into folio, which make us to >> use folio->_last_cpupid directly. > > What do you mean by "safe"? I think you mean "Does not increase the > size of struct page", but if that is what you mean, why not just say so? > If there's something else you mean, please explain.
Don't increase size of struct page and don't impact the real order of struct page as the above three archs without numa balancing support.
> > In any event, I'd like to see some reasoning that _last_cpupid is actually > information which is logically maintained on a per-allocation basis, > not a per-page basis (I think this is true, but I honestly don't know)
The _last_cpupid is updated in should_numa_migrate_memory() from numa fault(do_numa_page, and do_huge_pmd_numa_page), it is per-page(normal page and PMD-mapped page). Maybe I misunderstand your mean, please correct me.
> > And looking at all this, I think it makes sense to move _last_cpupid > before the kmsan garbage, then add both 'virtual' and '_last_cpupid' > to folio.
sure, I will add both of them into folio and don't re-order 'virtual' and '_last_cpupid'. > >
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