Re: [libvirt] [PATCH 2/2] Add -mem-shared option

+Markus On Tue, Dec 03, 2019 at 03:43:03PM +0100, Igor Mammedov wrote: > On Tue, 3 Dec 2019 09:56:15 +0100 > Thomas Huth <thuth(a)redhat.com&gt; wrote: > > > On 02/12/2019 22.00, Eduardo Habkost wrote: > > > On Mon, Dec 02, 2019 at 08:39:48AM +0100, Igor Mammedov wrote: > > >> On Fri, 29 Nov 2019 18:46:12 +0100 > > >> Paolo Bonzini <pbonzini(a)redhat.com&gt; wrote: > > >> > > >>> On 29/11/19 13:16, Igor Mammedov wrote: > > >>>> As for "-m", I'd make it just an alias that translates > > >>>> -m/mem-path/mem-prealloc > > >>> > > >>> I think we should just deprecate -mem-path/-mem-prealloc in 5.0. CCing > > >>> Thomas as mister deprecation. :) > > >> > > >> I'll add that to my series > > > > > > Considering that the plan is to eventually reimplement those > > > options as syntactic sugar for memory backend options (hopefully > > > in less than 2 QEMU releases), what's the point of deprecating > > > them? > > > > Well, it depends on the "classification" [1] of the parameter... > > > > Let's ask: What's the main purpose of the option? > > > > Is it easier to use than the "full" option, and thus likely to be used > > by a lot of people who run QEMU directly from the CLI? In that case it > > should stay as "convenience option" and not be deprecated. > > > > Or is the option merely there to give the upper layers like libvirt or > > some few users and their scripts some more grace period to adapt their > > code, but we all agree that the options are rather ugly and should > > finally go away? Then it's rather a "legacy option" and the deprecation > > process is the right way to go. Our QEMU interface is still way > > overcrowded, we should try to keep it as clean as possible. > > After switching to memdev for main RAM, users could use relatively > short global options > -global memory-backend.prealloc|share=on > and > -global memory-backend-file.mem-path=X|prealloc|share=on > > instead of us adding and maintaining slightly shorter > -mem-shared/-mem-path/-mem-prealloc Global properties are a convenient way to expose knobs through the command line with little effort, but we have no documentation on which QOM properties are really supposed to be touched by users using -global. Unless we fix the lack of documentation, I'd prefer to have syntactic sugar translated to -global instead of recommending direct usage of -global.