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Re: [PATCH v1 3/8] qcow2: add zstd cluster compression
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From: |
Vladimir Sementsov-Ogievskiy |
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Subject: |
Re: [PATCH v1 3/8] qcow2: add zstd cluster compression |
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Date: |
Thu, 27 Feb 2020 12:55:45 +0300 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 |
27.02.2020 10:29, Denis Plotnikov wrote:
zstd significantly reduces cluster compression time.
It provides better compression performance maintaining
the same level of the compression ratio in comparison with
zlib, which, at the moment, is the only compression
method available.
The performance test results:
Test compresses and decompresses qemu qcow2 image with just
installed rhel-7.6 guest.
Image cluster size: 64K. Image on disk size: 2.2G
The test was conducted with brd disk to reduce the influence
of disk subsystem to the test results.
The results is given in seconds.
compress cmd:
time ./qemu-img convert -O qcow2 -c -o compression_type=[zlib|zstd]
src.img [zlib|zstd]_compressed.img
decompress cmd
time ./qemu-img convert -O qcow2
[zlib|zstd]_compressed.img uncompressed.img
compression decompression
zlib zstd zlib zstd
------------------------------------------------------------
real 65.5 16.3 (-75 %) 1.9 1.6 (-16 %)
user 65.0 15.8 5.3 2.5
sys 3.3 0.2 2.0 2.0
Both ZLIB and ZSTD gave the same compression ratio: 1.57
compressed image size in both cases: 1.4G
Signed-off-by: Denis Plotnikov <address@hidden>
---
block/qcow2-threads.c | 122 +++++++++++++++++++++++++++++++++++++++++
block/qcow2.c | 7 +++
configure | 29 ++++++++++
docs/interop/qcow2.txt | 18 ++++++
qapi/block-core.json | 3 +-
5 files changed, 178 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 1c128e9840..e942c4d7e5 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -28,6 +28,11 @@
#define ZLIB_CONST
#include <zlib.h>
+#ifdef CONFIG_ZSTD
+#include <zstd.h>
+#include <zstd_errors.h>
+#endif
+
#include "qcow2.h"
#include "block/thread-pool.h"
#include "crypto.h"
@@ -164,6 +169,113 @@ static ssize_t qcow2_zlib_decompress(void *dest, size_t
dest_size,
return ret;
}
+#ifdef CONFIG_ZSTD
+
+#define ZSTD_LEN_BUF 4
+
+/*
+ * qcow2_zstd_compress()
+ *
+ * Compress @src_size bytes of data using zstd compression method
+ *
+ * @dest - destination buffer, @dest_size bytes
+ * @src - source buffer, @src_size bytes
+ *
+ * Returns: compressed size on success
This doesn't match qcow2_co_compress definition. You should return 0 on success.
+ * -ENOMEM destination buffer is not enough to store compressed data
+ * -EIO on any other error
+ */
+
+static ssize_t qcow2_zstd_compress(void *dest, size_t dest_size,
+ const void *src, size_t src_size)
+{
+ size_t ret;
+
+ /*
+ * steal ZSTD_LEN_BUF bytes in the very beginng of the buffer
beginning
+ * to store compressed chunk size
+ */
+ char *d_buf = ((char *) dest) + ZSTD_LEN_BUF;
+
+ /*
+ * sanity check that we can store the compressed data length,
+ * and there is some space left for the compressor buffer
+ */
+ if (dest_size <= ZSTD_LEN_BUF) {
+ return -ENOMEM;
+ }
+
+ dest_size -= ZSTD_LEN_BUF;
+
+ ret = ZSTD_compress(d_buf, dest_size, src, src_size, 5);
+
+ if (ZSTD_isError(ret)) {
+ if (ZSTD_getErrorCode(ret) == ZSTD_error_dstSize_tooSmall) {
+ return -ENOMEM;
+ } else {
+ return -EIO;
+ }
+ }
+
+ /* paraniod sanity check that we can store the commpressed size */
+ if (ret > UINT_MAX) {
+ return -ENOMEM;
+ }
I'd use UINT32_MAX, possibly even more paranoid)
+
+ /* store the compressed chunk size in the very beginning of the buffer */
+ stl_be_p(dest, ret);
+
+ return ret + ZSTD_LEN_BUF;
return 0;
+}
+
+/*
+ * qcow2_zstd_decompress()
+ *
+ * Decompress some data (not more than @src_size bytes) to produce exactly
+ * @dest_size bytes using zstd compression method
+ *
+ * @dest - destination buffer, @dest_size bytes
+ * @src - source buffer, @src_size bytes
+ *
+ * Returns: 0 on success
+ * -EIO on any error
+ */
+
extra empty line.
+static ssize_t qcow2_zstd_decompress(void *dest, size_t dest_size,
+ const void *src, size_t src_size)
+{
+ /*
+ * zstd decompress wants to know the exact length of the data.
+ * For that purpose, on compression, the length is stored in
+ * the very beginning of the compressed buffer
+ */
+ size_t s_size;
+ const char *s_buf = ((const char *) src) + ZSTD_LEN_BUF;
+
+ /*
+ * sanity check that we can read 4 byte the content length and
+ * and there is some content to decompress
+ */
+ if (src_size <= ZSTD_LEN_BUF) {
+ return -EIO;
+ }
+
+ s_size = ldl_be_p(src);
+
+ /* sanity check that the buffer is big enough to read the content from */
+ if (src_size - ZSTD_LEN_BUF < s_size) {
+ return -EIO;
+ }
+
+ if (ZSTD_isError(
+ ZSTD_decompress(dest, dest_size, s_buf, s_size))) {
hmm, it fit into one line actually
+ return -EIO;
+ }
+
+ return 0;
+}
+#endif
+
static int qcow2_compress_pool_func(void *opaque)
{
Qcow2CompressData *data = opaque;
@@ -215,6 +327,11 @@ qcow2_co_compress(BlockDriverState *bs, void *dest, size_t
dest_size,
fn = qcow2_zlib_compress;
break;
+#ifdef CONFIG_ZSTD
+ case QCOW2_COMPRESSION_TYPE_ZSTD:
+ fn = qcow2_zstd_compress;
+ break;
+#endif
default:
return -ENOTSUP;
}
@@ -247,6 +364,11 @@ qcow2_co_decompress(BlockDriverState *bs, void *dest,
size_t dest_size,
fn = qcow2_zlib_decompress;
break;
+#ifdef CONFIG_ZSTD
+ case QCOW2_COMPRESSION_TYPE_ZSTD:
+ fn = qcow2_zstd_decompress;
+ break;
+#endif
default:
return -ENOTSUP;
}
diff --git a/block/qcow2.c b/block/qcow2.c
index 2ccb2cabd1..9c8ad9d580 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1257,6 +1257,9 @@ static int validate_compression_type(BDRVQcow2State *s,
Error **errp)
switch (s->compression_type) {
case QCOW2_COMPRESSION_TYPE_ZLIB:
+#ifdef CONFIG_ZSTD
+ case QCOW2_COMPRESSION_TYPE_ZSTD:
+#endif
break;
default:
@@ -3506,6 +3509,10 @@ qcow2_co_create(BlockdevCreateOptions *create_options,
Error **errp)
}
switch (qcow2_opts->compression_type) {
+#ifdef CONFIG_ZSTD
+ case QCOW2_COMPRESSION_TYPE_ZSTD:
+ break;
+#endif
default:
error_setg_errno(errp, -EINVAL, "Unknown compression type");
goto out;
diff --git a/configure b/configure
index 48d6f89d57..4690a7ea9f 100755
--- a/configure
+++ b/configure
@@ -444,6 +444,7 @@ opengl_dmabuf="no"
cpuid_h="no"
avx2_opt=""
zlib="yes"
+zstd=""
capstone=""
lzo=""
snappy=""
@@ -1371,6 +1372,10 @@ for opt do
;;
--disable-lzfse) lzfse="no"
;;
+ --enable-zstd) zstd="yes"
+ ;;
+ --disable-zstd) zstd="no"
+ ;;
--enable-guest-agent) guest_agent="yes"
;;
--disable-guest-agent) guest_agent="no"
@@ -1829,6 +1834,7 @@ disabled with --disable-FEATURE, default is enabled if
available:
(for reading bzip2-compressed dmg images)
lzfse support of lzfse compression library
(for reading lzfse-compressed dmg images)
+ zstd support of zstd compression library
seccomp seccomp support
coroutine-pool coroutine freelist (better performance)
glusterfs GlusterFS backend
@@ -2453,6 +2459,25 @@ EOF
fi
fi
+#########################################
+# zstd check
+
+if test "$zstd" != "no" ; then
+ cat > $TMPC << EOF
+#include <zstd.h>
+int main(void) { ZSTD_versionNumber(); return 0; }
+EOF
+ if compile_prog "" "-lzstd" ; then
+ LIBS="$LIBS -lzstd"
+ zstd="yes"
+ else
+ if test "$zstd" = "yes"; then
+ feature_not_found "zstd" "Install libzstd-devel"
to correspond to style used around: s/libzstd-devel/libzstd devel/
+ fi
+ zstd="no"
+ fi
+fi
+
##########################################
# libseccomp check
@@ -6668,6 +6693,7 @@ echo "lzo support $lzo"
echo "snappy support $snappy"
echo "bzip2 support $bzip2"
echo "lzfse support $lzfse"
+echo "zstd support $zstd"
echo "NUMA host support $numa"
echo "libxml2 $libxml2"
echo "tcmalloc support $tcmalloc"
@@ -7559,6 +7585,9 @@ if test "$plugins" = "yes" ; then
"\$ld_exported_symbols_list should have been set to 'yes'."
fi
fi
+if test "$zstd" = "yes" ; then
+ echo "CONFIG_ZSTD=y" >> $config_host_mak
+fi
if test "$tcg_interpreter" = "yes"; then
QEMU_INCLUDES="-iquote \$(SRC_PATH)/tcg/tci $QEMU_INCLUDES"
diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
index 5597e24474..aeca2ddebd 100644
--- a/docs/interop/qcow2.txt
+++ b/docs/interop/qcow2.txt
@@ -208,6 +208,7 @@ version 2.
Available compression type values:
0: zlib <https://www.zlib.net/>
+ 1: zstd <http://github.com/facebook/zstd>
=== Header padding ===
@@ -575,11 +576,28 @@ Compressed Clusters Descriptor (x = 62 - (cluster_bits -
8)):
Another compressed cluster may map to the tail of the
final
sector used by this compressed cluster.
+ The layout of the compressed data depends on the compression
+ type used for the image (see compressed cluster layout).
+
If a cluster is unallocated, read requests shall read the data from the
backing
file (except if bit 0 in the Standard Cluster Descriptor is set). If there is
no backing file or the backing file is smaller than the image, they shall read
zeros for all parts that are not covered by the backing file.
+=== Compressed Cluster Layout ===
+
+The compressed cluster data has a layout depending on the compression
+type used for the image, as follows:
+
+Compressed data layout for the available compression types:
+(x = data_space_length - 1)
Note, that term 'data_space_lenght' is not defined in the spec..
Hmm. And it's not trivial to define it correctly, all we have is offset and
"number of additional sectors", and may be not all bytes of final sector are
occupied... What about something like this:
In the following layout description byte 0 corresponds to byte at host cluster
offset,
as defined by "Compressed Clusters Descriptor" paragraph above. The whole
layout occupy
space starting from this offset, using additional 512-byte sectors defined by
"Compressed Clusters Descriptor" paragraph, not necessarily occupying all of
the bytes
in the final sector. Let x be number of last byte of the layout.
+
+ 0: (default) zlib <http://zlib.net/>:
+ Byte 0 - x: the compressed data content
+ all the space provided used for compressed data
+ 1: zstd <http://github.com/facebook/zstd>:
+ Byte 0 - 3: the length of compressed data in bytes
+ 4 - x: the compressed data content
Maybe, note that x+! == 4 + length, where length is value of first field of the
layout.
== Snapshots ==
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 873fbef3b5..4b6e576c44 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4401,11 +4401,12 @@
# Compression type used in qcow2 image file
#
# @zlib: zlib compression, see <http://zlib.net/>
+# @zstd: zstd compression, see <http://github.com/facebook/zstd>
#
# Since: 5.0
##
{ 'enum': 'Qcow2CompressionType',
- 'data': [ 'zlib' ] }
+ 'data': [ 'zlib', { 'name': 'zstd', 'if': 'defined(CONFIG_ZSTD)' } ] }
##
# @BlockdevCreateOptionsQcow2:
--
Best regards,
Vladimir
[PATCH v1 4/8] iotests: filter out compression_type, Denis Plotnikov, 2020/02/27
[PATCH v1 1/8] qcow2: introduce compression type feature, Denis Plotnikov, 2020/02/27