linux-kernel - Re: [PATCH v4 0/6] LoongArch: Add pv ipi support on LoongArch VM

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Message-ID: <542a8f4e-cec3-92d0-1cdd-43d112eec605@loongson.cn>
Date: Thu, 22 Feb 2024 18:06:05 +0800
From: maobibo <maobibo@...ngson.cn>
To: WANG Xuerui <kernel@...0n.name>, Huacai Chen <chenhuacai@...nel.org>,
 Tianrui Zhao <zhaotianrui@...ngson.cn>, Juergen Gross <jgross@...e.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
 virtualization@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v4 0/6] LoongArch: Add pv ipi support on LoongArch VM



On 2024/2/22 下午5:34, WANG Xuerui wrote:
> On 2/17/24 11:15, maobibo wrote:
>> On 2024/2/15 下午6:25, WANG Xuerui wrote:
>>> On 2/15/24 18:11, WANG Xuerui wrote:
>>>> Sorry for the late reply (and Happy Chinese New Year), and thanks 
>>>> for providing microbenchmark numbers! But it seems the more 
>>>> comprehensive CoreMark results were omitted (that's also absent in 
>>>> v3)? While the 
>>>
>>> Of course the benchmark suite should be UnixBench instead of 
>>> CoreMark. Lesson: don't multi-task code reviews, especially not after 
>>> consuming beer -- a cup of coffee won't fully cancel the influence. ;-)
>>>
>> Where is rule about benchmark choices like UnixBench/Coremark for ipi 
>> improvement?
> 
> Sorry for the late reply. The rules are mostly unwritten, but in general 
> you can think of the preference of benchmark suites as a matter of 
> "effectiveness" -- the closer it's to some real workload in the wild, 
> the better. Micro-benchmarks is okay for illustrating the points, but 
> without demonstrating the impact on realistic workloads, a change could 
> be "useless" in practice or even decrease various performance metrics 
> (be that throughput or latency or anything that matters in the certain 
> case), but get accepted without notice.
yes, micro-benchmark cannot represent the real world, however it does 
not mean that UnixBench/Coremark should be run. You need to point out 
what is the negative effective from code, or what is the possible real 
scenario which may benefit. And points out the reasonable benchmark 
sensitive for IPIs rather than blindly saying UnixBench/Coremark.

Regards
Bibo Mao

>