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Re: [PATCH 0/4] target/ppc: Use probe_access
From: |
Richard Henderson |
Subject: |
Re: [PATCH 0/4] target/ppc: Use probe_access |
Date: |
Thu, 30 Jan 2020 08:09:39 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 |
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~
- [PATCH 0/4] target/ppc: Use probe_access, Richard Henderson, 2020/01/29
- [PATCH 1/4] target/ppc: Use probe_access for LSW, STSW, Richard Henderson, 2020/01/29
- [PATCH 2/4] target/ppc: Use probe_access for LMW, STMW, Richard Henderson, 2020/01/29
- [PATCH 3/4] target/ppc: Remove redundant mask in DCBZ, Richard Henderson, 2020/01/29
- [PATCH 4/4] target/ppc: Use probe_write for DCBZ, Richard Henderson, 2020/01/29
- Re: [PATCH 0/4] target/ppc: Use probe_access, Aleksandar Markovic, 2020/01/29
- Re: [PATCH 0/4] target/ppc: Use probe_access,
Richard Henderson <=
- Re: [PATCH 0/4] target/ppc: Use probe_access, Howard Spoelstra, 2020/01/30
- Re: [PATCH 0/4] target/ppc: Use probe_access, Howard Spoelstra, 2020/01/30
- Re: [PATCH 0/4] target/ppc: Use probe_access, David Gibson, 2020/01/30