From: Yulei Zhang <yuleixzhang@xxxxxxxxxxx> In current system each physical memory page is assocaited with a page structure which is used to track the usage of this page. But due to the memory usage rapidly growing in cloud environment, we find the resource consuming for page structure storage becomes highly remarkable. So is it an expense that we could spare? This patchset introduces an idea about how to save the extra memory through a new virtual filesystem -- dmemfs. Dmemfs (Direct Memory filesystem) is device memory or reserved memory based filesystem. This kind of memory is special as it is not managed by kernel and most important it is without 'struct page'. Therefore we can leverage the extra memory from the host system to support more tenants in our cloud service. We uses a kernel boot parameter 'dmem=' to reserve the system memory when the host system boots up, the details can be checked in /Documentation/admin-guide/kernel-parameters.txt. Theoretically for each 4k physical page it can save 64 bytes if we drop the 'struct page', so for guest memory with 320G it can save about 5G physical memory totally. Detailed usage of dmemfs is included in /Documentation/filesystem/dmemfs.rst. TODO: 1. we temporary disable the record_steal_time() before entering guest, will enable that after solve the conflict. 2. working on systemcall such as mincore, will update the status and patches soon. Yulei Zhang (35): fs: introduce dmemfs module mm: support direct memory reservation dmem: implement dmem memory management dmem: let pat recognize dmem dmemfs: support mmap dmemfs: support truncating inode down dmem: trace core functions dmem: show some statistic in debugfs dmemfs: support remote access dmemfs: introduce max_alloc_try_dpages parameter mm: export mempolicy interfaces to serve dmem allocator dmem: introduce mempolicy support mm, dmem: introduce PFN_DMEM and pfn_t_dmem mm, dmem: dmem-pmd vs thp-pmd mm: add pmd_special() check for pmd_trans_huge_lock() dmemfs: introduce ->split() to dmemfs_vm_ops mm, dmemfs: support unmap_page_range() for dmemfs pmd mm: follow_pmd_mask() for dmem huge pmd mm: gup_huge_pmd() for dmem huge pmd mm: support dmem huge pmd for vmf_insert_pfn_pmd() mm: support dmem huge pmd for follow_pfn() kvm, x86: Distinguish dmemfs page from mmio page kvm, x86: introduce VM_DMEM dmemfs: support hugepage for dmemfs mm, x86, dmem: fix estimation of reserved page for vaddr_get_pfn() mm, dmem: introduce pud_special() mm: add pud_special() to support dmem huge pud mm, dmemfs: support huge_fault() for dmemfs mm: add follow_pte_pud() dmem: introduce dmem_bitmap_alloc() and dmem_bitmap_free() dmem: introduce mce handler mm, dmemfs: register and handle the dmem mce kvm, x86: temporary disable record_steal_time for dmem dmem: add dmem unit tests Add documentation for dmemfs .../admin-guide/kernel-parameters.txt | 38 + Documentation/filesystems/dmemfs.rst | 59 + arch/x86/Kconfig | 1 + arch/x86/include/asm/pgtable.h | 32 +- arch/x86/include/asm/pgtable_types.h | 13 +- arch/x86/kernel/setup.c | 3 + arch/x86/kvm/mmu/mmu.c | 5 +- arch/x86/kvm/x86.c | 2 + arch/x86/mm/pat/memtype.c | 21 + drivers/vfio/vfio_iommu_type1.c | 4 + fs/Kconfig | 1 + fs/Makefile | 1 + fs/dmemfs/Kconfig | 16 + fs/dmemfs/Makefile | 8 + fs/dmemfs/inode.c | 1063 ++++++++++++++++ fs/dmemfs/trace.h | 54 + fs/inode.c | 6 + include/linux/dmem.h | 49 + include/linux/fs.h | 1 + include/linux/huge_mm.h | 5 +- include/linux/mempolicy.h | 3 + include/linux/mm.h | 9 + include/linux/pfn_t.h | 17 +- include/linux/pgtable.h | 22 + include/trace/events/dmem.h | 85 ++ include/uapi/linux/magic.h | 1 + mm/Kconfig | 21 + mm/Makefile | 1 + mm/dmem.c | 1075 +++++++++++++++++ mm/dmem_reserve.c | 303 +++++ mm/gup.c | 94 +- mm/huge_memory.c | 19 +- mm/memory-failure.c | 69 +- mm/memory.c | 74 +- mm/mempolicy.c | 4 +- mm/mprotect.c | 7 +- mm/mremap.c | 3 + tools/testing/dmem/Kbuild | 1 + tools/testing/dmem/Makefile | 10 + tools/testing/dmem/dmem-test.c | 184 +++ 40 files changed, 3336 insertions(+), 48 deletions(-) create mode 100644 Documentation/filesystems/dmemfs.rst create mode 100644 fs/dmemfs/Kconfig create mode 100644 fs/dmemfs/Makefile create mode 100644 fs/dmemfs/inode.c create mode 100644 fs/dmemfs/trace.h create mode 100644 include/linux/dmem.h create mode 100644 include/trace/events/dmem.h create mode 100644 mm/dmem.c create mode 100644 mm/dmem_reserve.c create mode 100644 tools/testing/dmem/Kbuild create mode 100644 tools/testing/dmem/Makefile create mode 100644 tools/testing/dmem/dmem-test.c -- 2.28.0
