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Message-ID: <4A0463D1.9090800@zytor.com>
Date: Fri, 08 May 2009 09:54:41 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Sam Ravnborg <sam@...nborg.org>
CC: "H. Peter Anvin" <hpa@...ux.intel.com>,
linux-kernel@...r.kernel.org, vgoyal@...hat.com, hbabu@...ibm.com,
kexec@...ts.infradead.org, ying.huang@...el.com, mingo@...e.hu,
tglx@...utronix.de, ebiederm@...ssion.com
Subject: Re: [PATCH 01/14] x86, boot: align the .bss section in the decompressor
Sam Ravnborg wrote:
>> }
>> + . = ALIGN(32);
>
> Where does this magic 32 comes from?
> I would assume the better choice would be:
> . = ALIGN(L1_CACHE_BYTES);
>
> So we match the relevant CPU.
>
> In general for alignmnet of output sections I see the need for:
> 1) Function call
> 2) L1_CACHE_BYTES
> 3) PAGE_SIZE
> 4) 2*PAGE_SIZE
>
> But I see magic constant used here and there that does not match
> the above (when looking at all archs).
> So I act when I see a new 'magic' number..
>
I picked 32 as being larger than the maximum known size that affects rep
performance, but L1_CACHE_BYTES really would make more sense, you're right.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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