Subject: Re: [PATCH] clocksource: Store reg field within struct clocksource
To: Thomas Gleixner <tglx@linutronix.de>,
        Russell King - ARM Linux <linux@arm.linux.org.uk>
CC: 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>
References: <564C8086.80804@sigmadesigns.com>
 <20151118172114.GS8644@n2100.arm.linux.org.uk>
 <alpine.DEB.2.11.1511191130480.3898@nanos>
 <20151119103645.GV8644@n2100.arm.linux.org.uk>
 <alpine.DEB.2.11.1511191137320.3898@nanos>
 <20151119110842.GX8644@n2100.arm.linux.org.uk>
 <alpine.DEB.2.11.1511191209000.3898@nanos>
From: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Message-ID: <564DC006.8000406@sigmadesigns.com>
Date: Thu, 19 Nov 2015 13:26:46 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:41.0) Gecko/20100101
 Firefox/41.0 SeaMonkey/2.38
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.11.1511191209000.3898@nanos>
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1456
Lines: 46

On 19/11/2015 12:14, Thomas Gleixner wrote:

> So yes, the alignment of the clocksource struct is not longer
> relevant. The case where we access clocksource->max_cycles is when
> CONFIG_DEBUG_TIMEKEEPING is enabled, which imposes worse performance
> problems to timekeeping than the extra cacheline.
> 
> So the simple solution for this issue is indeed the one liner below.

It would make sense to also remove the comment emphasizing the
alignment requirement.

Regards.

8<-------------------

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 278dd279a7a8..6a0f86a9a92d 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -64,10 +64,6 @@ struct module;
  * @owner:             module reference, must be set by clocksource in modules
  */
 struct clocksource {
-       /*
-        * Hotpath data, fits in a single cache line when the
-        * clocksource itself is cacheline aligned.
-        */
        cycle_t (*read)(struct clocksource *cs);
        cycle_t mask;
        u32 mult;
@@ -95,7 +91,7 @@ struct clocksource {
        cycle_t wd_last;
 #endif
        struct module *owner;
-} ____cacheline_aligned;
+};
 
 /*
  * Clock source flags bits::

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/