From: Junyan He <junyan...@intel.com> The nvdimm size is huge, sometimes it is more than 256G or even more. This is a huge burden for snapshot saving. One snapshot point with nvdimm may occupy more than 50G disk space even with compression enabled. We need to introduce dependent snapshot manner to solve this problem. The first snapshot point should always be saved completely, and enable dirty log trace after saving for nvdimm memory region. The later snapshot point should add the reference to previous snapshot's nvdimm data and just saving dirty pages. This can save a lot of disk and time if the snapshot operations are triggered frequently. We add save_snapshot_dependency functions to QCOW2 file system firstly, the later snapshot will add reference to previous dependent snapshot's data cluster. There is an alignment problem here, the dependent data should always be cluster aligned. We need to add some padding data when saving the snapshot to make it always cluster aligned. The logic between nvdimm and ram for snapshot saving is a little confused now, we need to exclude nvdimm kind memory region from ram list and the dirty log tracing setting is also not very clear. Maybe we can separate the snapshot saving from the migration logic later to make code clean. In theory, this kind of manner can apply to any kind of memory. But because it need to turn dirty log trace on, the performance may decline. So we just enable it for nvdimm kind memory firstly.
Signed-off-by: Junyan He <junyan...@intel.com> --- Makefile.target | 1 + block/qcow2-snapshot.c | 154 ++++++++++++++++++++++ block/qcow2.c | 2 + block/qcow2.h | 7 + block/snapshot.c | 45 +++++++ exec.c | 7 + hw/ppc/spapr.c | 2 +- hw/s390x/s390-stattrib.c | 2 +- include/block/block_int.h | 9 ++ include/block/snapshot.h | 7 + include/exec/memory.h | 9 ++ include/exec/ram_addr.h | 2 + include/migration/misc.h | 4 + include/migration/register.h | 2 +- include/migration/snapshot.h | 3 + memory.c | 18 ++- migration/block.c | 2 +- migration/nvdimm.c | 1033 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ migration/qemu-file.c | 61 +++++++++ migration/qemu-file.h | 14 ++ migration/ram.c | 19 ++- migration/savevm.c | 62 ++++++++- vl.c | 1 + 23 files changed, 1452 insertions(+), 14 deletions(-)
