Message-ID: <5074756C.8070502@intel.com>
Date: Tue, 09 Oct 2012 12:05:16 -0700
From: Alexander Duyck <alexander.h.duyck@intel.com>
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To: Andi Kleen <andi@firstfloor.org>
CC: konrad.wilk@oracle.com, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, rob@landley.net, akpm@linux-foundation.org,
        joerg.roedel@amd.com, bhelgaas@google.com, shuahkhan@gmail.com,
        linux-kernel@vger.kernel.org, devel@linuxdriverproject.org,
        x86@kernel.org, torvalds@linux-foundation.org
Subject: Re: [RFC PATCH 0/7] Improve swiotlb performance by using physical
 addresses
References: <20121004002113.5016.66913.stgit@gitlad.jf.intel.com> <m28vbkx3hw.fsf@firstfloor.org> <506F3670.4020202@intel.com> <20121005200245.GQ16230@one.firstfloor.org> <506F6BF2.8030500@intel.com> <20121006175751.GS16230@one.firstfloor.org> <5072F497.2000703@intel.com>
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On 10/08/2012 08:43 AM, Alexander Duyck wrote:
> On 10/06/2012 10:57 AM, Andi Kleen wrote:
>> BTW __pa used to be a simple subtraction, the if () was just added to
>> handle the few call sites for x86-64 that do __pa(&text_symbol).
>> Maybe we should just go back to the old __pa_symbol() for those cases,
>> then __pa could be the simple subtraction it used to was again
>> and it could be inlined and everyone would be happy.
>>
>> -Andi
> What I am probably looking at doing is splitting the function in two as
> you suggest where we have a separate function for the text symbol case. 
> I will probably also take the 32 bit approach and add a debug version
> that is still a separate function for uses such as determining if we
> have any callers who should be using __pa_symbol instead of __pa.
>
> Thanks,
>
> Alex

I gave up on trying to split __pa and __pa_symbol.   Yesterday I
realized there is way too much code that depends on the two resolving to
the same function, and many cases are pretty well hidden.  Instead I
just mailed out a patch that inlines an optimized version of
__phys_addr.  I figure it is probably as good as it is going to get
without having to rip the entire x86 portion of the kernel apart to
separate uses of __pa and __pa_symbol.

Thanks,

Alex
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