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Re: [PATCH] MIPS: Define __arch_swab64 for all mips r2 cpus (v2).

To: David Daney <>
Subject: Re: [PATCH] MIPS: Define __arch_swab64 for all mips r2 cpus (v2).
From: Ralf Baechle <>
Date: Wed, 1 Jul 2009 19:20:51 +0100
Cc: "Maciej W. Rozycki" <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <> <>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Jun 30, 2009 at 06:13:41PM -0700, David Daney wrote:

> The problem with CPU_MIPS64_R2 in the kernel is that it means two  
> unrelated things:
> 1) The cpu can execute all mips64r2 ISA instructions.
> 2) The cpu requires that all worse case cache and execution hazards are  
> handled.
> In the case of the Octeon processors, #1 is true, but we can get better  
> performance by omitting many of the hazard barriers because they are  
> unneeded.

The most performance sensitive hazard barriers are the ones in the TLB
exception handlers and they're now being handled in C code in tlbex.c
which mostly does runtime decissions.  I suspect the remaining hazard
barriers are not a big performance thing anymore.


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