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Date: Tue, 21 Dec 2004 00:11:06 +0100
From: Fabrice Bellard <fabrice@bellard.org>
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Subject: Re: [Qemu-devel] Re: [PATCH] CONFIG_MMU_MAP powerpc host support
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To: Piotras <piotras@gmail.com>, qemu-devel@nongnu.org

Piotras wrote:
> Great!
> 
> Do you have an estimate of possible performance gain by introducing 
> direct pointer to mmu_map for memory read?
> 
> I have two ideas for future experimentation.
> 
> There is a trick possible without wasting another register for global 
> variable: use two copies of CPUState (one for privileged and another 
> for user mode), then make mmu_map.add_read first member of the 
> struct. This would introduce guest register coping for user/supervisor 
> switch, but maybe performance gain would justify this.
> Another idea: if we could align add_read/add_write on 64k boundary, 
> "addi" could be removed.

IMHO, using a single global register and interleaving the 4 access types 
is the best solution...

Fabrice.