On Tue 09-10-18 14:00:34, Mel Gorman wrote: > On Tue, Oct 09, 2018 at 02:27:45PM +0200, Michal Hocko wrote: > > [Sorry for being slow in responding but I was mostly offline last few > > days] > > > > On Tue 09-10-18 10:48:25, Mel Gorman wrote: > > [...] > > > This goes back to my point that the MADV_HUGEPAGE hint should not make > > > promises about locality and that introducing MADV_LOCAL for specialised > > > libraries may be more appropriate with the initial semantic being how it > > > treats MADV_HUGEPAGE regions. > > > > I agree with your other points and not going to repeat them. I am not > > sure madvise s the best API for the purpose though. We are talking about > > memory policy here and there is an existing api for that so I would > > _prefer_ to reuse it for this purpose. > > > > I flip-flopped on that one in my head multiple times on the basis of > how strict it should be. Memory policies tend to be black or white -- > bind here, interleave there, etc. It wasn't clear to me what the best > policy would be to describe "allocate local as best as you can but allow > fallbacks if necessary". I was thinking about MPOL_NODE_PROXIMITY with the following semantic: - try hard to allocate from a local or very close numa node(s) even when that requires expensive operations like the memory reclaim/compaction before falling back to other more distant numa nodes. > Hence, I started leaning towards advise as it is > really about advice that the kernel can ignore if necessary. That said, > I don't feel as strongly about the "how" as I do about the fact that > applications and libraries should not depend on side-effects of the > MADV_HUGEPAGE implementation that relate to locality. completely agreed on this. -- Michal Hocko SUSE Labs
