Re: [Qemu-block] [PATCH 2/3] qcow2: add option to clean unused cache entries after some time

[Alberto Garcia]

On Thu 28 May 2015 05:23:40 PM CEST, Max Reitz wrote:

>>>> Can we mark the parameter optional, and only provide it when it is
>>>> non-zero?  That way, qemu-img (which cannot set an interval) will
>>>> not report it, and the only time it will appear is if it was set as
>>>> part of opening the block device under qemu.

>>> That sounds good.

>> But what do we do with the other parameters (refcount-cache-size,
>> l2-cache-size)? We cannot have the same solution there because they
>> don't belong to the image file either, and they're never going go be
>> zero.

> Of course, the simplest solution is to worry about cache-clean-interval 
> for now and worry about the cache sizes later… But that basically means 
> "We'll never worry about them unless someone complains", so…

My worry is that the solution works in this case because the default
value happens to be 0 and means "disabled", so it makes sense, but it
doesn't work in general with other parameters, so we would be adding
something that we know it's ad-hoc.

Berto