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Tue, 10 Dec 2019 13:09:50 +0000 (UTC) Date: Tue, 10 Dec 2019 14:09:49 +0100 From: Igor Mammedov To: Markus Armbruster Subject: Re: [PATCH 2/2] Add -mem-shared option Message-ID: <20191210140949.4a1c3ff2@redhat.com> In-Reply-To: <87tv6831vr.fsf@dusky.pond.sub.org> References: <20191128172807.788e6aeb@redhat.com> <20191129110703.2b15c541@redhat.com> <04dadf85-cd35-fd37-9642-8087cba625bd@redhat.com> <20191129131652.6683b769@redhat.com> <528bb183-3d44-e541-8765-9c0e01f23157@redhat.com> <20191202083948.3e8bb134@redhat.com> <20191202210057.GQ14595@habkost.net> <1ff4cc6a-0ec8-96ff-1e39-e682429852e4@redhat.com> <20191203154303.035c33b3@redhat.com> <20191209205840.GJ498046@habkost.net> <87tv6831vr.fsf@dusky.pond.sub.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: tgQg54HoPMWJUmbzbSbYVg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Eduardo Habkost , libvir-list@redhat.com, QEMU , =?UTF-8?B?TWFyYy1B?= =?UTF-8?B?bmRyw6k=?= Lureau , Stefan Hajnoczi , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 10 Dec 2019 11:34:32 +0100 Markus Armbruster wrote: > Eduardo Habkost 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 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 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. I can document concrete globals as replacement at the place -mem-path/-mem-prealloc are documented during deprecation and then in 2 releases we will just drop legacy syntax and keep only globals over there. (eventually it will spread various globals over man page, which I don't like but we probably should start somwhere and consolidate later if globals in man page become normal practice.)