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Date: Sun, 31 Dec 2000 19:10:46 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Andi Kleen <ak@suse.de>, Geert Uytterhoeven <geert@linux-m68k.org>,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: test13-pre5
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In-Reply-To: <Pine.LNX.4.10.10012310924500.4029-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Sun, Dec 31, 2000 at 09:27:23AM -0800
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On Sun, Dec 31, 2000 at 09:27:23AM -0800, Linus Torvalds wrote:
> The alpha systems I remember this problem on were all [..]

Yes the granularity issue has nothing to do with SMP (with preemptive kernel
it can trigger even without interrupts involved into the code). Also
CONFIG_SPACE_EFFICIENT looks not necessary.

The x8 name is confusing IMHO (when I read `8' I expect 8bits only, the x
isn't explicit enough). But by using a better name we could save some byte on
alpha ev6 and x86. Something like granular_char/granular_short/granular_int
looks nicer.  For the generic 64bit cpu they needs to be _unconditionally_
defined to `long'.

BTW, only old chips (ev[45]) doesn't provide byte granularity. Infact a linux
kernel compiled for ev6 can handle byte granularity also on alpha (it uses
-mcpu=ev6).

alpha reference manual 5.2.2:

	[..] For each region, an implementation must support aligned quadword
	access and may optionally support aligned longword access or byte
	access. If byte access is supported in a region, aligned word access
	and aligned longword access are also supported. [..]

21264hrm:

	[..] The 21264-generated external references to memory space are
	always of a fixed 64-byte size, though the internal access granularity
	is byte, word, longword, or quad-word. [..]

Andrea
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