On 2 Oct 2020, at 3:50, David Hildenbrand wrote: >>>> - huge page sizes controllable by the userspace? >>> >>> It might be good to allow advanced users to choose the page sizes, so they >>> have better control of their applications. >> >> Could you elaborate more? Those advanced users can use hugetlb, right? >> They get a very good control over page size and pool preallocation etc. >> So they can get what they need - assuming there is enough memory. >> > > I am still not convinced that 1G THP (TGP :) ) are really what we want > to support. I can understand that there are some use cases that might > benefit from it, especially: > > "I want a lot of memory, give me memory in any granularity you have, I > absolutely don't care - but of course, more TGP might be good for > performance." Say, you want a 5GB region, but only have a single 1GB > hugepage lying around. hugetlbfs allocation will fail. > > > But then, do we really want to optimize for such (very special?) use > cases via " 58 files changed, 2396 insertions(+), 460 deletions(-)" ? I am planning to further refactor my code to reduce the size and make it more general to support any size of THPs. As Matthew’s patchset[1] is removing kernel’s THP size assumption, it might be a good time to make THP support more general. > > I think gigantic pages are a sparse resource. Only selected applications > *really* depend on them and benefit from them. Let these special > applications handle it explicitly. > > Can we have a summary of use cases that would really benefit from this > change? For large machine learning applications, 1GB pages give good performance boost[2]. NVIDIA DGX A100 box now has 1TB memory, which means 1GB pages are not that sparse in GPU-equipped infrastructure[3]. In addition, @Roman Gushchin should be able to provide a more concrete story from his side. [1] https://lore.kernel.org/linux-mm/20200908195539.25896-1-willy@xxxxxxxxxxxxx/ [2] http://learningsys.org/neurips19/assets/papers/18_CameraReadySubmission_MLSys_NeurIPS_2019.pdf [3] https://www.nvidia.com/content/dam/en-zz/Solutions/Data-Center/nvidia-dgx-a100-datasheet.pdf — Best Regards, Yan Zi
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