linux-kernel - Re: [PATCH 08/25] hrtimer: Reduce conditional code (expires_next, next

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Message-ID: <alpine.DEB.2.20.1709281005130.1885@nanos>
Date:   Thu, 28 Sep 2017 10:07:52 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Anna-Maria Gleixner <anna-maria@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Christoph Hellwig <hch@....org>, keescook@...omium.org,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH 08/25] hrtimer: Reduce conditional code (expires_next,
 next_timer)

On Tue, 26 Sep 2017, Peter Zijlstra wrote:

> On Thu, Aug 31, 2017 at 12:23:37PM -0000, Anna-Maria Gleixner wrote:
> > The hrtimer_cpu_base struct member expires_next and next_timer are
> > conditional members (CONFIG_HIGH_RES_TIMERS). This makes the hrtimer code
> > more complex and harder to understand than it actually is.
> > 
> > Reduce the conditionals related to those two struct members.
> 
> So this grows the data structure for !HIGH_RES for easier code? We no
> longer care about archs that don't support HIGH_RES?

We care, but there is a tradeoff between the required conditional code and
the marginal storage overhead. Easier to follow code which does a few
superflous things for the !highres case is certainly preferred.

Thanks,

	tglx