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

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.