Extend the list of formats to include "sparse", which uses QEMU's mapped-ram stream format [1] to write guest memory blocks at fixed offsets in the save image file. [1] https://gitlab.com/qemu-project/qemu/-/blob/master/docs/devel/migration/mapped-ram.rst?ref_type=heads Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx> --- src/qemu/qemu.conf.in | 9 ++++++++- src/qemu/qemu_saveimage.c | 2 ++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in index d853136f10..ab9725e40d 100644 --- a/src/qemu/qemu.conf.in +++ b/src/qemu/qemu.conf.in @@ -588,11 +588,18 @@ # disk space when saving large memory guests. Various compression formats are # available for specifying a save image compressed by the named algorithm. # Supported compression formats are "zstd", "lzop", "gzip", "bzip2", and "xz". +# The "sparse" format uses QEMU's mapped-ram stream format to write guest memory +# blocks at fixed offsets in the save image file. # save_image_format can be used to select the desired save format. "raw" is # the traditional format used by libvirt and is also the default. The # compression formats can be used to save disk space, although this typically -# results in longer save and restore times. +# results in longer save and restore times. The "sparse" format results in a +# save image file that is roughly the logical size of the guest's memory, +# although on-disk size is a function of guest memory usage. The "sparse" +# format is useful when a predictable maximum save image file size is +# needed. The other formats can result in a save image file much larger +# than guest memory if the guest runs a memory intensive workload. # # save_image_format is used with 'virsh save' or 'virsh managedsave'. It is # an error if the specified save_image_format is not valid, or cannot be diff --git a/src/qemu/qemu_saveimage.c b/src/qemu/qemu_saveimage.c index 69617e07eb..ff5b9e72eb 100644 --- a/src/qemu/qemu_saveimage.c +++ b/src/qemu/qemu_saveimage.c @@ -48,6 +48,7 @@ typedef enum { QEMU_SAVE_FORMAT_XZ = 3, QEMU_SAVE_FORMAT_LZOP = 4, QEMU_SAVE_FORMAT_ZSTD = 5, + QEMU_SAVE_FORMAT_SPARSE = 6, /* Note: add new members only at the end. These values are used in the on-disk format. Do not change or re-use numbers. */ @@ -64,6 +65,7 @@ VIR_ENUM_IMPL(qemuSaveFormat, "xz", "lzop", "zstd", + "sparse", ); static inline void -- 2.43.0
