linux-kernel - Re: [PATCH] sched/doc: supplement CPU capacity with RISC-V

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Date:   Mon, 27 Feb 2023 12:55:54 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Song Shuai <suagrfillet@...il.com>
CC:     <corbet@....net>, <alexs@...nel.org>, <siyanteng@...ngson.cn>,
        <robh@...nel.org>, <palmer@...osinc.com>,
        <leyfoon.tan@...rfivetech.com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] sched/doc: supplement CPU capacity with RISC-V

On Mon, Feb 27, 2023 at 12:40:45PM +0000, Song Shuai wrote:
> Conor Dooley <conor.dooley@...rochip.com> 于2023年2月27日周一 11:57写道：
> >
> > On Mon, Feb 27, 2023 at 06:59:41PM +0800, Song Shuai wrote:
> > > This commit 7d2078310cbf ("dt-bindings: arm: move cpu-capacity to a
> > > shared loation") updates some references about capacity-dmips-mhz
> >
> > Not requesting a respin for this, but mentioning commit 991994509ee9
> > ("dt-bindings: riscv: add a capacity-dmips-mhz cpu property") is
> > probably more relevant as a justification for this change.
> >
> Thanks for your correction, I'll pay attention next time.
> 
> I have a question about the patch you mentioned:
> The patch uses cpu_scale per_cpu variable to store the CPU capacity
> through arch_topology,
> But arch_scale_cpu_capacity() interface seems not defined to deliver
> the cpu_scale to the scheduler
> In contrast, arm64 defines it as the topology_get_cpu_scale() in its
> arch/arm64/include/asm/topology.h.
> Is this an oversight or a particular purpose?

Intentional oversight I suppose? It wasn't my intention to do anything
other than document the property that people were already using in
their devicetrees (and finding bugs with!).
In retrospect, perhaps it is better if I un-review this patch until
we know it is plumbed into the scheduler properly?

Ley Foon Tan is the one that found the RISC-V bugs with this property in
their devicetree, so perhaps they've already done the work here?

Thanks,
Conor.

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