linux-kernel - Re: [PATCH v2 0/8] scheduler tinification

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Date:   Tue, 13 Jun 2017 09:12:28 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 0/8] scheduler tinification


* Nicolas Pitre <nicolas.pitre@...aro.org> wrote:

> > A series that shrinks the .text size of the allnoconfig core Linux kernel from 1MB 
> > to 9.9MB in isolation is not proof.
> 
> I assume you meant 0.9MB.

0.992 MB actually if we apply the ~8k .text savings. 0.9MB would imply 100k of 
savings on an allnoconfig kernel.

> It is no proof of course. But I'm following the well known and proven 
> "release early, release often" mantra here... unless this is no longer 
> promoted?

I'm following that same pattern: I gave you negative review feedback as early as 
possible. Fragmention of the scheduler ABI increases complexity and has knock-on 
costs - and the kernel size reduction for the usecase you cited are still 1-2 
orders of magnitude away from making a practical difference.

> > There will literally have to be two orders of magnitude more patches than that 
> > to reach the 32K size envelope, if I (very) optimistically assume that the 
> > difficulty to shrink code is constant (which it most certainly is not).
> 
> Once again, my goal is _not_ 32KB.
> 
> And I don't intend to shrink code. Most of the time I just want to 
> _remove_ code. Compiling it out to be precise. The goal of this series 
> is all about compiling out code. And to achieve that with the scheduler, 
> I simply moved some code to different source files and not including 
> those source files in the final build. That keeps the number of #ifdef's 
> to a minimum but it makes a big diffstat due to the code movement.

So I'm fine with most of the code movement - let's try this series without any of 
the more controversial bits which should make future arguments easier.

Thanks,

	Ingo