Am 30.06.2017 um 15:01 hat Alberto Garcia geschrieben: > On Tue 27 Jun 2017 06:31:45 PM CEST, Kevin Wolf wrote: > > * Speaking of recursion: ImageInfo recursively includes information > > about all images in the backing chain. This is what makes the output > > of query-named-block-nodes so redundant. It is also inconsistent > > because the runtime information (BlockInfo/BlockDeviceInfo) isn't > > recursive. > > I've also been told of cases where a query-block command on a VM with a > very large amount of images in all backing chains would slow down the > guest because of this recursion. > > I haven't been able to reproduce this problem myself, but being able to > see only the devices seen by the guest (as opposed to the complete > graph) seems like a good idea.
I think the information only really becomes redundant if you use query-named-block-nodes because then you list every backing file node and each of them contains the recursive information. With query-block, you start at the top and include the information for each image in the backing file chain only once. If we did indeed have a problem there, that might mean that we do in fact need filtering to reduce the overhead. But I don't think any of the information involves any I/O to get, so it seems unlikely to me that this would make a big difference. Kevin