linux-kernel - Re: [PATCH V2] riscv: export cpu/freq invariant to scheduler

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Date:   Mon, 27 Mar 2023 12:49:44 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Song Shuai <suagrfillet@...il.com>
CC:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <linux-riscv@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <bjorn@...nel.org>
Subject: Re: [PATCH V2] riscv: export cpu/freq invariant to scheduler

+CC Bjorn,

On Thu, Mar 23, 2023 at 08:39:24PM +0800, Song Shuai wrote:
> RISC-V now manages CPU topology using arch_topology which provides
> CPU capacity and frequency related interfaces to access the cpu/freq
> invariant in possible heterogeneous or DVFS-enabled platforms.
> 
> Here adds topology.h file to export the arch_topology interfaces for
> replacing the scheduler's constant-based cpu/freq invariant accounting.
> 
> Signed-off-by: Song Shuai <suagrfillet@...il.com>

Something in CI really, really doesn't like this patch:
https://patchwork.kernel.org/project/linux-riscv/patch/20230323123924.3032174-1-suagrfillet@gmail.com/

The CI stuff applies the patch, builds the tree, resets to HEAD~1,
builds it again, goes back to the applied patch and builds a third time.
Builds 2 and 3 are incremental.
In theory the same stuff should change between applying and removing the
patch, and therefore each of builds 2 and 3 should have the same coverage,
but that doesn't seem to be happening here.
Build 2 looks to have rebuilt almost nothing and build 3 has rebuilt the
world.
I'm gonna chalk that one down as a CI issue rather than your patch!

That said, I was wondering if you would end up submitting this patch,
given the discussion on your last one ;)

Looks to be the same as was done for arm64, so fwiw:
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

> ---
> changes from V1:
>   - fix the leading underscore and tidy the patch up 
> ---
>  arch/riscv/include/asm/topology.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>  create mode 100644 arch/riscv/include/asm/topology.h
> 
> diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h
> new file mode 100644
> index 000000000000..727e8d163a3b
> --- /dev/null
> +++ b/arch/riscv/include/asm/topology.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_RISCV_TOPOLOGY_H
> +#define _ASM_RISCV_TOPOLOGY_H
> +
> +#include <linux/arch_topology.h>
> +
> +/* Replace task scheduler's default frequency-invariant accounting */
> +#define arch_scale_freq_tick	topology_scale_freq_tick
> +#define arch_set_freq_scale	topology_set_freq_scale
> +#define arch_scale_freq_capacity	topology_get_freq_scale
> +#define arch_scale_freq_invariant	topology_scale_freq_invariant
> +
> +/* Replace task scheduler's default cpu-invariant accounting */
> +#define arch_scale_cpu_capacity	topology_get_cpu_scale
> +
> +/* Enable topology flag updates */
> +#define arch_update_cpu_topology	topology_update_cpu_topology
> +
> +#include <asm-generic/topology.h>
> +#endif /* _ASM_RISCV_TOPOLOGY_H */
> -- 
> 2.20.1
> 
> 

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