[libvirt] [PATCH v4 1/2] conf, docs: Add qcow2 cache configuration support

[Liu Qing]

On Thu, Sep 14, 2017 at 10:02:40AM +0200, Peter Krempa wrote:
> On Thu, Sep 14, 2017 at 09:29:28 +0200, Peter Krempa wrote:
> > On Thu, Sep 14, 2017 at 13:02:46 +0800, Liu Qing wrote:
> > > On Wed, Sep 13, 2017 at 01:20:03PM +0200, Peter Krempa wrote:
> > > > On Wed, Sep 13, 2017 at 17:21:23 +0800, Liu Qing wrote:
> > 
> > [...]
> > 
> > > > [1] There's discussion I can link to for other tuning parameters. The
> > > > gist is that allowing users to set something withoug giving them
> > > > guidance is pointless since they might not use it. Also if the guidance
> > > > is strict (e.g. a formula, libvirt or qemu should set the defaults
> > > > properly and not force users to do the calculation)
> > > The guidance could be found in doc/qcow2-cache.txt in qemu source code.
> > > As John Ferlan suggested I have added the file locaton in formatdomain.html.in. 
> > 
> > Well, if the guidance is absolute (use this cache size and it's okay)
> > then we should implement it automatically (don't allow users
> > to set it.)
> 
> One more thing. The design you've proposed is really not user friendly.
> The user has to read a lenghty document, then inquire the parameters for
> every single qcow2 image, do the calculations and set it in the XML.
> This might be okay for higher level management tools, but not for users
> who use libvirt directly.
I agree this is not user friendly. I only give the user a choice, maybe
not the best, right now. Any suggestion will be greatly appreicated.
For our company, this feature will be an add-on to Openstack.