Re: [PATCH 0/4] target/ppc: Use probe_access

[Richard Henderson]

On 1/29/20 5:35 PM, Aleksandar Markovic wrote:
> 00:51 Čet, 30.01.2020. Richard Henderson <address@hidden
> <mailto:address@hidden>> је написао/ла:
>>
>> The first two address the performance regression noticed
>> by Howard Spoelstra.  The last two are just something I
>> noticed at the same time.
>>
> 
> But, performance regression, according to Howard bisect analysis, happened
> because of the change in target-independant code, and the fix presented here 
> is
> in target-specific code. This defies basic logic and deserves clear and
> detailed explanation.
> 
> My additional concern, of course, is: Are other targets exposed to performance
> degradation, and why?

Potentially, yes.  However:

It requires lots of loads in a loop, on a hot path.  I would not have guessed
that the ppc32 Load Multiple Word (et al) was on a hot path at all, since the
instructions are deprecated.  But that's what an ancient os gets you, I suppose.


r~