Re: [Qemu-devel] [PATCH 8/8] docs: document how to configure the qcow2 L2/refcount caches

[Alberto Garcia]

On Mon 11 May 2015 03:23:25 PM CEST, Max Reitz <address@hidden> wrote:

>> +   disk_size = l2_cache_size * cluster_size / 8
>> +   disk_size = refcount_cache_size * cluster_size / 2
>
> Only with the default of refcount_bits=16. In the general case, it's
> refcount_cache_size * cluster_size * 8 / refcount_bits.

I actually omitted that on purpose because I didn't want to go into too
many details and I hadn't realized that it's now possible to configure
refcount_bits. I will correct the document.

I wonder what happens then to this DEFAULT_L2_REFCOUNT_SIZE_RATIO of 4,
because that's only valid if refcount_bits == 16.

Is the user supposed to calculate that ratio manually and configure both
cache sizes?

> Apart from this minor thing, looks good. Well, except that maybe it
> should be preferred to use .qcow2 as the extension for qcow2 files
> (instead of .img).

Sure, I can change that too.

Berto