On 2023/1/18 0:13, Jiri Denemark wrote:
On Tue, Jan 17, 2023 at 21:58:39 +0800, Jiang Jiacheng wrote:
On 2023/1/17 16:44, Claudio Fontana wrote:
Hi,
On 1/16/23 14:42, Jiang Jiacheng wrote:
Add public API VIR_MIGRATE_PARAM_PARALLEL_COMPRESSION, VIR_MIGRATE_PARAM_PARALLEL_ZLIB_LEVEL, VIR_MIGRATE_PARAM_PARALLEL_ZSTD_LEVEL for migration APIs to support set compression method and compress level used during migration.
Signed-off-by: Jiang Jiacheng <jiangjiacheng@huawei.com>
we don't know what drivers other than QEMU are going to implement in terms of algorithms, and we also don't know what new algorithms QEMU will come up with in the future,
Indeed, what you're talking about is better and more scalable. These patches only adapt to the three parameters of the current version QEMU，and some commits on the QEMU side may be required to support this mode.
I should fix that we don't need commits in QEMU to implement in this way.
so I was told when I was working on something similar (but not identical), for the "multifd save restore prototype" to try to make it more general.
First of all, maybe we don't need two different _LEVEL parameters, just a VIR_MIGRATE_PARAM_PARALLEL_COMPRESSION_LEVEL, which is then mapped in the qemu driver to the specific correct QEMU parameter according to the chosen algo.
Since QEMU sets different parameters for different compression methods, I've added two corresponding parameters here. If the qemu side does not change, we can use the same virsh option to input the compression level and pass the expected QEMU parameters according to the input compression method on the libvirt side.
same here.
Then the VIR_MIGRATE_PARAM_PARALLEL_COMPRESSION could be a freeform string, that is then interpreted by each driver, for example "zlib", or "zstd" in this case. So other drivers can pass different strings, and QEMU future new compression algorithms will not need changes to libvirt at all.
I think what you mean is we can input any string to VIR_MIGRATE_PARAM_PARALLEL_COMPRESSION and whether it is available is judged by QEMU or other emulators. It is supported with these patches, we can use any string for this parameter, though QEMU only support 'none', 'zlib','zstd' for it, and other input will return with an error.
I think we should just be able to use the existing VIR_MIGRATE_PARAM_COMPRESSION to specify the method. We know whether we're asking for parallel migration from VIR_MIGRATE_PARALLEL flag. We might need to add checks for which compression methods are only allowed with/without VIR_MIGRATE_PARALLEL.
I see, I will try this way and add necessary check for them in next version.
On the other hand, for consistency reasons I think we should add separate VIR_MIGRATE_PARAM_COMPRESSION_ZLIB_LEVEL and VIR_MIGRATE_PARAM_COMPRESSION_ZSTD_LEVEL even though they are the same. The other two compressions methods we currently support (mt and xbzrle) have each their own set of parameters.
If so, shall we keeping using separate virsh migrate options(like --comp-zlib-level and --comp-zstd-level)? Or just use one option (--parallel-comp-level) to pass compression level, according to the compression method we have chosen? Thanks Jiang Jiacheng
Jirka