Re: [libvirt] [PATCH 12/12] getstats: start crawling backing chain for qemu

Wire up backing chain recursion. Note that for now, we just use the same allocation numbers for read-only backing files as what offline domains would report. It is not the correct allocation number for qcow2 over block devices during block-commit, and it misses out on the fact that qemu also reports read statistics on backing files that are worth knowing about (seriously - for a thin-provisioned setup, it would be nice to easily get at a count of how many reads were serviced from the backing file in relation to reads serviced by the active layer). But it is at least sufficient to prove that the algorithm is working, and to let other people start coding to the interface while waiting for later patches that get the correct information.

For a running domain, where one of the two images has a backing file, I see the traditional output: $ virsh domstats --block testvm2 Domain: 'testvm2' block.count=2 block.0.name=vda block.0.path=/tmp/wrapper.qcow2 block.0.rd.reqs=1 block.0.rd.bytes=512 block.0.rd.times=28858 block.0.wr.reqs=0 block.0.wr.bytes=0 block.0.wr.times=0 block.0.fl.reqs=0 block.0.fl.times=0 block.0.allocation=0 block.0.capacity=1310720000 block.0.physical=200704 block.1.name=vdb block.1.path=/dev/sda7 block.1.rd.reqs=0 block.1.rd.bytes=0 block.1.rd.times=0 block.1.wr.reqs=0 block.1.wr.bytes=0 block.1.wr.times=0 block.1.fl.reqs=0 block.1.fl.times=0 block.1.allocation=0 block.1.capacity=1310720000 vs. the new output: $ virsh domstats --block --backing testvm2 Domain: 'testvm2' block.count=3 block.0.name=vda block.0.path=/tmp/wrapper.qcow2 block.0.rd.reqs=1 block.0.rd.bytes=512 block.0.rd.times=28858 block.0.wr.reqs=0 block.0.wr.bytes=0 block.0.wr.times=0 block.0.fl.reqs=0 block.0.fl.times=0 block.0.allocation=0 block.0.capacity=1310720000 block.0.physical=200704 block.1.name=vda block.1.path=/dev/sda6 block.1.backingIndex=1 block.1.allocation=1073741824 block.1.capacity=1310720000 block.1.physical=1073741824 block.2.name=vdb block.2.path=/dev/sda7 block.2.rd.reqs=0 block.2.rd.bytes=0 block.2.rd.times=0 block.2.wr.reqs=0 block.2.wr.bytes=0 block.2.wr.times=0 block.2.fl.reqs=0 block.2.fl.times=0 block.2.allocation=0 block.2.capacity=1310720000

* src/qemu/qemu_driver.c (QEMU_DOMAIN_STATS_BACKING): New internal enum bit. (qemuConnectGetAllDomainStats): Recognize new user flag, and pass details to... (qemuDomainGetStatsBlock): ...here, where we can do longer recursion. (qemuDomainGetStatsOneBlock): Output new field. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- src/qemu/qemu_driver.c | 55 +++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 46 insertions(+), 9 deletions(-)