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

Eduardo Habkost <ehabkost(a)redhat.com&gt; writes: > +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. Fair point. I'd take QOM property documentation over still more sugar. Sometimes, the practical way to make simple things simple is sugar. I can accept that. This doesn't look like such a case, though.