Message-ID: <50A6C6DB.2000205@zytor.com>
Date: Fri, 16 Nov 2012 15:06:03 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Steven Rostedt <rostedt@goodmis.org>
CC: Alexander Duyck <alexander.h.duyck@intel.com>, tglx@linutronix.de,
        mingo@redhat.com, andi@firstfloor.org,
        Frederic Weisbecker <fweisbec@gmail.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 6/8] x86/ftrace: Use __pa_symbol instead of __pa on
 C visible symbols
References: <20121116214644.8521.79072.stgit@ahduyck-cp1.jf.intel.com>  <20121116215718.8521.24026.stgit@ahduyck-cp1.jf.intel.com>  <1353104456.7586.27.camel@gandalf.local.home>  <a162a888-9892-43ca-ad17-61c19936c6f4@email.android.com> <1353105926.7586.30.camel@gandalf.local.home>
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On 11/16/2012 02:45 PM, Steven Rostedt wrote:
>
> #define __pa(x)		__phys_addr((unsigned long)(x))
> #define __pa_symbol(x)	__pa(__phys_reloc_hide((unsigned long)(x)))
>
> I'm confused. __pa_symbol() just calls __pa() with some macro magic to
> its parameter. How is this a performance improvement?
>

One of the earlier patches in this series changes __pa_symbol() to avoid 
the conditional hidden inside __phys_addr(), since by definition a 
symbol can only be on one side of that branch.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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