Re: [Qemu-devel] [PATCH 2/9] S/390 CPU emulation

[Ulrich Hecht]

On Thursday 22 October 2009, Aurelien Jarno wrote:
> Probably the second. Changing the instruction pointer in the helper
> instead of using the proper goto_tb TCG op prevents TB chaining, and
> therefore as a huge impact on performance.
>
> It's something not difficult to implement, and that I would definitely
> want to see in the patch before getting it merged.

OK, I implemented it, and the surprising result is that performance  does 
not get any better; in fact it even suffers a little bit. (My standard 
quick test, the polarssl test suite, shows about a 2% performance impact 
when profiled with cachegrind).

Could there be anything I overlooked? I modelled my implementation after 
those in the existing targets. (See the attached patch that goes on top 
of my other S/390 patches.)

CU
Uli

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s390-goto_tb.patch
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