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Wysocki" Cc: Peter Zijlstra , Greg KH , Linux Kernel Mailing List , Linux PM , Thomas Gleixner , Ingo Molnar , Borislav Petkov , the arch/x86 maintainers , "H. Peter Anvin" , Sudeep Holla , Viresh Kumar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Benjamin Segall , Mel Gorman , "Luis R. Rodriguez" , Kees Cook , Iurii Zaikin , Frederic Weisbecker , Todd Kjos , "Cc: Android Kernel" Subject: Re: [PATCH 00/14] Modularize schedutil Message-ID: <20200512151120.GB101124@google.com> References: <20200508111612.GA252673@google.com> <20200508113141.GB5298@hirez.programming.kicks-ass.net> <20200508130507.GA10541@google.com> <20200511090049.GA229633@google.com> <20200512092102.GA16151@google.com> <20200512135813.GA101124@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tuesday 12 May 2020 at 16:08:56 (+0200), Rafael J. Wysocki wrote: > If some piece of kernel code is modular, it still needs to be build. > The difference is when and how it gets loaded, so can you possibly > elaborate here? Sure thing, sorry if that wasn't clear. The end goal with GKI is the following: Google will release a single binary kernel image (signed, etc etc) that all devices using a given Android version will be required to use. That image is however going to be only for the core of the kernel (no drivers or anything of the sort). Vendors and OEMs, on their end, will be responsible to build and ship GKI-compatible modules for their respective devices. So, Android devices will eventually ship with a Google-issued GKI, plus a bunch of vendor-provided modules loaded during boot. This is a significant shift from the current model where vendors completely own the kernel, and are largely free to use the kernel config they want. Today, those who don't use schedutil are free to turn the config off, for example. But GKI changes that. The 'core' GKI config is effectively imposed to the entire ecosystem. As of now, because it is 'bool' we have no choice but to compile schedutil in the core GKI as some (most) partners use it. But as you can imagine, that is not the preferred option of those who _don't_ use schedutil. Modularizing avoids any potential friction since the vendors who want to use it will be able load the module, and the others will simply not. That really is the reason for that series. Then there is an important question: why should upstream care about all that stuff? That's obviously debatable, but my biased opinion is that GKI is a good thing(TM). It's our opportunity to put some order in the android ecosystem and to reduce the delta with mainline. That'll definitely take time, and there will be Android-specific churn in GKI in the beginning, but we'd like to keep that as small as possible, and to converge to 0 looking forwards. I hope that helps! Thanks, Quentin