Based-on: <20221213213850.1481858-1-pet...@redhat.com> [PATCH 0/5] migration: Fix disorder of channel creations
Trees for reference: https://github.com/xzpeter/linux/releases/tag/doublemap-v0.1 https://github.com/xzpeter/qemu/releases/tag/doublemap-v0.1 This is an RFC series that only for early discussion purpose but not for merging. This patchset allows postcopy to work with huge pages better by migrating huge pages in small page sizes. It relies on a kernel feature called "hugetlb HGM" which is currently proposed on the Linux kernel mailing list by James Houghton, latest version v1: https://lore.kernel.org/r/20230105101844.1893104-1-jthough...@google.com [PS: The kernel v1 patchset may need a few fixups to make QEMU work, which are all contained in the tree link provided tagged doublemap-v0.1 above] The kernel series is still during review upstream, so the API is still not stable. I kept the old name of "doublemap" in this QEMU patchset to represent HGM. With that, huge pages can be mapped with even smaller sizes than the huge page itself. It can drastically reduce page fault latencies during postcopy if the guest has hugepage backed memories and make postcopy start working with huge pages. The average page request latency can drop from ~1sec to ~250us for 1G backed in the initial test results. UFFDIO_COPY doesn't support mapping huge pages in small sizes, so one major part of this series introduced UFFDIO_CONTINUE to resolve page faults for hugetlb mappings. Sampled page latency histogram for 18G guest with/without doublemap (preempt=on, single thread busy spin workload over 18G map): Before: @delay_us: [64, 128) 3 |@ | [128, 256) 84 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [256, 512) 10 |@@@@@@ | [512, 1K) 1 | | [1K, 2K) 0 | | [2K, 4K) 0 | | [4K, 8K) 0 | | [8K, 16K) 0 | | [16K, 32K) 0 | | [32K, 64K) 0 | | [64K, 128K) 0 | | [128K, 256K) 0 | | [256K, 512K) 0 | | [512K, 1M) 0 | | [1M, 2M) 17 |@@@@@@@@@@ | [2M, 4M) 21 |@@@@@@@@@@@@@ | [4M, 8M) 8 |@@@@ | [8M, 16M) 4 |@@ | After: @delay_us: [16, 32) 6 | | [32, 64) 6 | | [64, 128) 3117 |@@ | [128, 256) 70815 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@| [256, 512) 30460 |@@@@@@@@@@@@@@@@@@@@@@ | [512, 1K) 1135 | | [1K, 2K) 34 | | [2K, 4K) 42 | | [4K, 8K) 126 | | [8K, 16K) 91 | | [16K, 32K) 0 | | [32K, 64K) 1 | | Any early comment welcomed. Thanks. Peter Xu (21): update linux headers util: Include osdep.h first in util/mmap-alloc.c physmem: Add qemu_ram_is_hugetlb() madvise: Include linux/mman.h under linux-headers/ madvise: Add QEMU_MADV_SPLIT madvise: Add QEMU_MADV_COLLAPSE ramblock: Cache file offset for file-backed ramblocks ramblock: Cache the length to do file mmap() on ramblocks ramblock: Add RAM_READONLY ramblock: Add ramblock_file_map() migration: Add hugetlb-doublemap cap migration: Introduce page size for-migration-only migration: Add migration_ram_pagesize_largest() migration: Map hugetlbfs ramblocks twice, and pre-allocate migration: Teach qemu about minor faults and doublemap migration: Enable doublemap with MADV_SPLIT migration: Rework ram discard logic for hugetlb double-map migration: Allow postcopy_register_shared_ufd() to fail migration: Add postcopy_mark_received() migration: Handle page faults using UFFDIO_CONTINUE migration: Collapse huge pages again after postcopy finished backends/hostmem-file.c | 3 +- hw/virtio/vhost-user.c | 9 +- include/exec/cpu-common.h | 3 +- include/exec/memory.h | 4 +- include/exec/ram_addr.h | 6 +- include/exec/ramblock.h | 14 + include/qemu/madvise.h | 18 ++ include/standard-headers/drm/drm_fourcc.h | 63 +++- include/standard-headers/linux/ethtool.h | 81 ++++- include/standard-headers/linux/fuse.h | 20 +- .../linux/input-event-codes.h | 4 + include/standard-headers/linux/pci_regs.h | 2 + include/standard-headers/linux/virtio_blk.h | 19 ++ include/standard-headers/linux/virtio_bt.h | 8 + include/standard-headers/linux/virtio_net.h | 4 + linux-headers/asm-arm64/kvm.h | 1 + linux-headers/asm-generic/hugetlb_encode.h | 26 +- linux-headers/asm-generic/mman-common.h | 4 + linux-headers/asm-mips/mman.h | 4 + linux-headers/asm-riscv/kvm.h | 7 + linux-headers/asm-x86/kvm.h | 11 +- linux-headers/linux/kvm.h | 32 +- linux-headers/linux/psci.h | 14 + linux-headers/linux/userfaultfd.h | 4 + linux-headers/linux/vfio.h | 278 +++++++++++++++++- migration/migration.c | 56 +++- migration/migration.h | 1 + migration/postcopy-ram.c | 228 +++++++++++--- migration/postcopy-ram.h | 5 +- migration/ram.c | 165 ++++++++++- migration/ram.h | 2 + migration/trace-events | 6 +- qapi/migration.json | 7 +- softmmu/memory.c | 8 +- softmmu/physmem.c | 92 ++++-- util/mmap-alloc.c | 2 +- 36 files changed, 1051 insertions(+), 160 deletions(-) -- 2.37.3
