[PATCH 0/5] qemu: Introduce control of qcow2 metadata cache maximum size

[Peter Krempa]

On Thu, Jan 07, 2021 at 22:11:42 +0100, Ján Tomko wrote:
> On a Thursday in 2021, Peter Krempa wrote:
> > See patch 3/5 for explanation.
> > 
> > Peter Krempa (5):
> >  virDomainDiskDefFormatDriver: Rename 'driverBuf' to 'attrBuf'
> >  virDomainSnapshotDiskDefFormat: Use virXMLFormatElement
> >  conf: Introduce <metadata_cache> subelement of <disk><driver>
> >  conf: snapshot: Add support for <metadata_cache>
> >  qemu: Implement '<metadata_cache><max_size>' control for qcow2
> > 
> > docs/formatdomain.rst                         | 43 ++++++++++
> > docs/formatsnapshot.html.in                   |  4 +
> > docs/schemas/domaincommon.rng                 | 20 ++++-
> > docs/schemas/domainsnapshot.rng               | 10 ++-
> > src/conf/domain_conf.c                        | 81 ++++++++++++++-----
> > src/conf/snapshot_conf.c                      | 50 ++++++++----
> > src/qemu/qemu_block.c                         | 11 +++
> > src/qemu/qemu_domain.c                        | 15 ++++
> > src/qemu/qemu_snapshot.c                      | 14 ++++
> > src/util/virstoragefile.c                     |  1 +
> > src/util/virstoragefile.h                     |  2 +
> > .../qcow2-metadata-cache.xml                  | 14 ++++
> > .../qcow2-metadata-cache.xml                  | 18 +++++
> > tests/qemudomainsnapshotxml2xmltest.c         |  3 +
> > .../disk-metadata-cache.x86_64-latest.args    | 57 +++++++++++++
> > .../qemuxml2argvdata/disk-metadata-cache.xml  | 46 +++++++++++
> > tests/qemuxml2argvtest.c                      |  1 +
> > .../disk-metadata-cache.x86_64-latest.xml     | 58 +++++++++++++
> > tests/qemuxml2xmltest.c                       |  1 +
> > 19 files changed, 411 insertions(+), 38 deletions(-)
> > create mode 100644 tests/qemudomainsnapshotxml2xmlin/qcow2-metadata-cache.xml
> > create mode 100644 tests/qemudomainsnapshotxml2xmlout/qcow2-metadata-cache.xml
> > create mode 100644 tests/qemuxml2argvdata/disk-metadata-cache.x86_64-latest.args
> > create mode 100644 tests/qemuxml2argvdata/disk-metadata-cache.xml
> > create mode 100644 tests/qemuxml2xmloutdata/disk-metadata-cache.x86_64-latest.xml
> > 
> 
> Okay, so IIUC the difference to the previous attempts [0] is that this
> series that were rejected is, that this only uses 'cache-size' instead

Yes. Specifically, we now declare it as a metadata cache size maximum
size knob. This comes also with a change in qemu which allocates the
cache on-demand.