On Fri 20-11-20 14:43:04, Muchun Song wrote: [...] Thanks for improving the cover letter and providing some numbers. I have only glanced through the patchset because I didn't really have more time to dive depply into them. Overall it looks promissing. To summarize. I would prefer to not have the feature enablement controlled by compile time option and the kernel command line option should be opt-in. I also do not like that freeing the pool can trigger the oom killer or even shut the system down if no oom victim is eligible. One thing that I didn't really get to think hard about is what is the effect of vmemmap manipulation wrt pfn walkers. pfn_to_page can be invalid when racing with the split. How do we enforce that this won't blow up? I have also asked in a previous version whether the vmemmap manipulation should be really unconditional. E.g. shortlived hugetlb pages allocated from the buddy allocator directly rather than for a pool. Maybe it should be restricted for the pool allocation as those are considered long term and therefore the overhead will be amortized and freeing path restrictions better understandable. > Documentation/admin-guide/kernel-parameters.txt | 9 + > Documentation/admin-guide/mm/hugetlbpage.rst | 3 + > arch/x86/include/asm/hugetlb.h | 17 + > arch/x86/include/asm/pgtable_64_types.h | 8 + > arch/x86/mm/init_64.c | 7 +- > fs/Kconfig | 14 + > include/linux/bootmem_info.h | 78 +++ > include/linux/hugetlb.h | 19 + > include/linux/hugetlb_cgroup.h | 15 +- > include/linux/memory_hotplug.h | 27 - > mm/Makefile | 2 + > mm/bootmem_info.c | 124 ++++ > mm/hugetlb.c | 163 ++++- > mm/hugetlb_vmemmap.c | 765 ++++++++++++++++++++++++ > mm/hugetlb_vmemmap.h | 103 ++++ I will need to look closer but I suspect that a non-trivial part of the vmemmap manipulation really belongs to mm/sparse-vmemmap.c because the split and remapping shouldn't really be hugetlb specific. Sure hugetlb knows how to split but all the splitting should be implemented in vmemmap proper. > mm/memory_hotplug.c | 116 ---- > mm/sparse.c | 5 +- > 17 files changed, 1295 insertions(+), 180 deletions(-) > create mode 100644 include/linux/bootmem_info.h > create mode 100644 mm/bootmem_info.c > create mode 100644 mm/hugetlb_vmemmap.c > create mode 100644 mm/hugetlb_vmemmap.h Thanks! -- Michal Hocko SUSE Labs
