On Fri, Jan 08, 2021 at 13:13:30 +0000, Daniel Berrange wrote:
On Thu, Jan 07, 2021 at 03:59:36PM +0100, Peter Krempa wrote:
In certain specific cases it might be beneficial to be able to control the metadata caching of storage image format drivers of a hypervisor.
Introduce XML machinery to set the maximum size of the metadata cache which will be used by qemu's qcow2 driver.
Signed-off-by: Peter Krempa <pkrempa@redhat.com> --- docs/formatdomain.rst | 43 ++++++++++++++ docs/schemas/domaincommon.rng | 20 ++++++- src/conf/domain_conf.c | 51 ++++++++++++++-- src/util/virstoragefile.c | 1 + src/util/virstoragefile.h | 2 + .../qemuxml2argvdata/disk-metadata-cache.xml | 46 +++++++++++++++ .../disk-metadata-cache.x86_64-latest.xml | 58 +++++++++++++++++++ tests/qemuxml2xmltest.c | 1 + 8 files changed, 216 insertions(+), 6 deletions(-) create mode 100644 tests/qemuxml2argvdata/disk-metadata-cache.xml create mode 100644 tests/qemuxml2xmloutdata/disk-metadata-cache.x86_64-latest.xml
+ <disk type='file' device='disk'> + <driver name='qemu' type='qcow2' cache='none'/> + <source file='/tmp/QEMUGuest2.img'/> + <backingStore type='file'> + <format type='qcow2'> + <metadata_cache> + <max_size unit='kiB'>1024</max_size> + </metadata_cache>
I only wonder if this is uneccessarily verbose XML nesting ?
I actually had the same feeling, but adding it just as an attribute to <disk><driver ... >(the other case besides <backingStore> felt worse since we have a huge list of attributes there. I specifically want that it points to metadata cache maximum size so that there isn't any unnecessary ambiguity. Possibilities are to merge the <max_size> subelement into the parent element so that we decrease the amount of lines. Or possibly go with Jano's suggestion of dropping 'size' since that is obvious when unit='' is present (but note that unit is optional on input).