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

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Date: Thu, 15 Feb 2024 18:11:14 +0800
From: WANG Xuerui <kernel@...0n.name>
To: Bibo Mao <maobibo@...ngson.cn>, 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

Hi,

On 2/1/24 11:19, Bibo Mao wrote:
> [snip]
>
> Here is the microbenchmarck data with perf bench futex wake case on 3C5000
> single-way machine, there are 16 cpus on 3C5000 single-way machine, VM
> has 16 vcpus also. The benchmark data is ms time unit to wakeup 16 threads,
> the performance is higher if data is smaller.
> 
> perf bench futex wake, Wokeup 16 of 16 threads in ms
> --physical machine--   --VM original--   --VM with pv ipi patch--
>    0.0176 ms               0.1140 ms            0.0481 ms
> 
> ---
> Change in V4:
>    1. Modfiy pv ipi hook function name call_func_ipi() and
> call_func_single_ipi() with send_ipi_mask()/send_ipi_single(), since pv
> ipi is used for both remote function call and reschedule notification.
>    2. Refresh changelog.
> 
> Change in V3:
>    1. Add 128 vcpu ipi multicast support like x86
>    2. Change cpucfg base address from 0x10000000 to 0x40000000, in order
> to avoid confliction with future hw usage
>    3. Adjust patch order in this patchset, move patch
> Refine-ipi-ops-on-LoongArch-platform to the first one.

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 
changes between v4 and v2 shouldn't be performance-sensitive IMO (I 
haven't checked carefully though), it could be better to showcase the 
improvements / non-harmfulness of the changes and make us confident in 
accepting the changes.

-- 
WANG "xen0n" Xuerui

Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/