On 05.02.19 10:08, Denis Plotnikov wrote: > The patch adds some preparation parts for incompatible compression type > feature into QCOW2 header that indicates that *all* compressed clusters > must be (de)compressed using a certain compression type. > > It is implied that the compression type is set on the image creation and > can be changed only later by image convertion, thus the only compression > algorithm is used for the image. > > The plan is to add support for ZSTD and then may be something more effective > in the future. > > ZSDT compression algorithm consumes 3-5 times less CPU power with a > comparable comression ratio with zlib. It would be wise to use it for > data compression f.e. for backups. > > The default compression is ZLIB. > > Signed-off-by: Denis Plotnikov <dplotni...@virtuozzo.com> > --- > block/qcow2.c | 25 +++++++++++++++++++++++++ > block/qcow2.h | 26 ++++++++++++++++++++++---- > 2 files changed, 47 insertions(+), 4 deletions(-)
Are there plans to pursue this further?
[...]
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 32cce9eee2..fdde5bbefd 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -112,6 +112,10 @@
> #define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
> #define QCOW2_OPT_CACHE_CLEAN_INTERVAL "cache-clean-interval"
>
> +/* Compression types */
> +#define QCOW2_COMPRESSION_TYPE_ZLIB 0
> +#define QCOW2_COMPRESSION_TYPE_ZSTD 1
We probably want QAPI types anyway (qemu-img info should report the
compression type), so I think we could use them instead.
> typedef struct QCowHeader {
> uint32_t magic;
> uint32_t version;
> @@ -197,10 +201,13 @@ enum {
>
> /* Incompatible feature bits */
> enum {
> - QCOW2_INCOMPAT_DIRTY_BITNR = 0,
> - QCOW2_INCOMPAT_CORRUPT_BITNR = 1,
> - QCOW2_INCOMPAT_DIRTY = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
> - QCOW2_INCOMPAT_CORRUPT = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
> + QCOW2_INCOMPAT_DIRTY_BITNR = 0,
> + QCOW2_INCOMPAT_CORRUPT_BITNR = 1,
> + QCOW2_INCOMPAT_COMPRESSION_TYPE_BITNR = 2,
> + QCOW2_INCOMPAT_DIRTY = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
> + QCOW2_INCOMPAT_CORRUPT = 1 <<
> QCOW2_INCOMPAT_CORRUPT_BITNR,
> + QCOW2_INCOMPAT_COMPRESSION_TYPE =
> + 1 <<
> QCOW2_INCOMPAT_COMPRESSION_TYPE_BITNR,
>
> QCOW2_INCOMPAT_MASK = QCOW2_INCOMPAT_DIRTY
> | QCOW2_INCOMPAT_CORRUPT,
This mask needs to be expanded by QCOW2_INCOMPAT_COMPRESSION_TYPE.
> @@ -256,6 +263,10 @@ typedef struct Qcow2BitmapHeaderExt {
> uint64_t bitmap_directory_offset;
> } QEMU_PACKED Qcow2BitmapHeaderExt;
>
> +typedef struct Qcow2CompressionTypeExt {
> + uint32_t compression_type;
> +} QEMU_PACKED Qcow2CompressionTypeExt;
> +
> typedef struct BDRVQcow2State {
> int cluster_bits;
> int cluster_size;
> @@ -340,6 +351,13 @@ typedef struct BDRVQcow2State {
>
> CoQueue compress_wait_queue;
> int nb_compress_threads;
> + /**
> + * Compression type used for the image. Default: 0 - ZLIB
> + * The image compression type is set on image creation.
> + * The only way to change the compression type is to convert the image
> + * with the desired compresion type set
*compression
And, well, ideally qemu-img amend could perform this operation, too.
Max
> + */
> + uint32_t compression_type;
> } BDRVQcow2State;
>
> typedef struct Qcow2COWRegion {
>
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