Re: [PATCH 1/3] Add public API for parallel compression method

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(a)huawei.com&gt; > > 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. > 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. > 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.