[RFC common/manager/qemu-server 0/3] fix #1989: qemu: add qcow2 cache options

[Erik Fastermann <e.fastermann@proxmox.com>]

Hi all,

I'm interested in feedback for my patches fixing #1989 [0], which add multiple
options to configure the qcow2 L2/refcount cache. This enables huge performance
gains in some cases.

I tested this for the current and older QEMU machine versions and while a VM was
running. The add disk (vm creation and otherwise), import disk and edit disk
dialogs were considered.

I also have the following questions:

- Currently I also check the file extension is qcow2, because in many cases the
  disk format is currently not available (especially on the frontend). Is this
  good enough in general?

- The cache size input on the frontend is currently in bytes, because fine
  control might be required in some cases, but this is a little bit ugly.
  Is there a better way to do this?

- Should the ability to control cluster_size and refcount_bits be included in
  this patch or should a separate bug be created? There was some discussion
  about this on Bugzilla [0].

- Should minimum / maximum values be defined for all options and in what way?

- Should we validate that the cache sizes are multiples of the cluster size /
  cache entry size?

- I'm using oneOf for the cache_size to support the 'based-on-disk' variant, but
  this does not play nice with the generated Rust API types (currently set the
  outer type to string, but this probably does not work). Should this be changed
  or the Rust generation extended or can I use a custom enum on the Rust side?

- Should any extra documentation be added for this feature?

Thanks for your feedback!

Best,
Erik

[0] https://bugzilla.proxmox.com/show_bug.cgi?id=1989


pve-common:

Erik Fastermann (1):
  json schema: display nested oneOf error messages

 src/PVE/JSONSchema.pm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


qemu-server:

Erik Fastermann (1):
  fix #1989: disk: add qcow2 cache options

 src/PVE/QemuServer.pm          | 33 ++++++++++++
 src/PVE/QemuServer/Blockdev.pm | 33 ++++++++++++
 src/PVE/QemuServer/Drive.pm    | 99 ++++++++++++++++++++++++++++++++++
 3 files changed, 165 insertions(+)


pve-manager:

Erik Fastermann (1):
  fix #1989: qemu: disk: add cache size config

 www/manager6/Parser.js      |  2 +-
 www/manager6/qemu/HDEdit.js | 70 +++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)


Summary over all repositories:
  6 files changed, 238 insertions(+), 3 deletions(-)

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