On Thu, Sep 15, 2011 at 08:53:35AM +0100, Daniel P. Berrange wrote:
On Thu, Sep 15, 2011 at 03:31:48PM +0800, Hu Tao wrote:
+ +/** + * virDomainBlkioWeightDeviceParseXML + * + * this function parses a XML node: + * + * <device> + * <major>major</major> + * <minor>minor</minor> + * <weight>weight</weight> + * </device> + * + * and fills a virBlkioWeightDevice struct. + */
I'm not really seeing the benefit in using major, minor in the XML for this. The <disk> element is using the /dev/hda1 path for the host device, so I'd expect the same path to be usable for the block I/O tuning.
How does the scope work here, does major,minor have to refer to a block device, or can it refer to a partition ? If we have multiple <device> elements, each giving a different partition on the same device can we set different weight for each partition ?
blkio doesn't support io control on a partition, so I add major, minor to refer to a block device as a whole, rather than utilizing the existing <disk> element.
Hmm, well I think we should still just use the '/dev/hda' block device path. The major/minor numbers cannot be assumed to be stable across different hosts, so would break migration. Whereas you can use the /dev/disk/by-{id,path} symlinks for block paths and thus be migration safe.
Good idea. Thanks for the suggestion. To summarize, the XML describing weight_device like this will be acceptable: <device> <id>by-id</id> (or path here) <weight>weight</weight> </device> Should the <device> be changed into <disk> to remind user that the id is in fact a disk id? -- Thanks, Hu Tao