Short term, assuming there wouldn't be an objection from the libvirt community, I think spawning a thread pool and concurrently executing several rbd_stat calls concurrently would be the easiest and cleanest solution. I wouldn't suggest trying to roll your own solution for retrieving image sizes for format 1 and 2 RBD images directly within libvirt.
Longer term, given this use case, perhaps it would make sense to add an async version of rbd_open. The rbd_stat call itself just reads the data from memory initialized by rbd_open. On the Jewel branch, librbd has had some major rework and image loading is asynchronous under the hood already. -- Jason Dillaman ----- Original Message ----- > From: "Wido den Hollander" <w...@42on.com> > To: email@example.com > Sent: Monday, December 28, 2015 8:48:40 AM > Subject: Speeding up rbd_stat() in libvirt > > Hi, > > The storage pools of libvirt know a mechanism called 'refresh' which > will scan a storage pool to refresh the contents. > > The current implementation does: > * List all images via rbd_list() > * Call rbd_stat() on each image > > Source: > http://libvirt.org/git/?p=libvirt.git;a=blob;f=src/storage/storage_backend_rbd.c;h=cdbfdee98505492407669130712046783223c3cf;hb=master#l329 > > This works, but a RBD pool with 10k images takes a couple of minutes to > scan. > > Now, Ceph is distributed, so this could be done in parallel, but before > I start on this I was wondering if somebody had a good idea to fix this? > > I don't know if it is allowed in libvirt to spawn multiple threads and > have workers do this, but it was something which came to mind. > > libvirt only wants to know the size of a image and this is now stored in > the rbd_directory object, so the rbd_stat() is required. > > Suggestions or ideas? I would like to have this process to be as fast as > possible. > > Wido > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html