Date: Wed, 18 Nov 2015 17:21:15 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>, Mans Rullgard <mans@mansr.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Nicolas Pitre <nico@linaro.org>, Tony Lindgren <tony@atomide.com>,
        Sebastian Frias <sebastian_frias@sigmadesigns.com>
Subject: Re: [PATCH] clocksource: Store reg field within struct clocksource
Message-ID: <20151118172114.GS8644@n2100.arm.linux.org.uk>
References: <564C8086.80804@sigmadesigns.com>
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On Wed, Nov 18, 2015 at 02:43:34PM +0100, Marc Gonzalez wrote:
> Since 'struct clocksource' is ____cacheline_aligned, gcc must insert
> a lot of padding between reg and clksrc in 'struct clocksource_mmio'
> (for example, L1_CACHE_BYTES = 64 on ARMv7).
> 
> Storing reg within 'struct clocksource' removes unnecessary padding,
> and reg can then be grouped with other hot data. A nice side-effect
> of this patch is making container_of() unnecessary, which makes the
> code a bit simpler.
> 
> On 32-bit platforms, reg fits in the padding between read and mask,
> meaning no downside from storing it there.

Just swap the order of 'reg' and 'clksrc'.

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