[RFC PATCH] riscv: export cpu/freq invariant to scheduler

[RFC PATCH] riscv: export cpu/freq invariant to scheduler

[Song Shuai]

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@gmail.com>
---
 arch/riscv/include/asm/topology.h | 19 +++++++++++++++++++
 1 file changed, 19 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..14bbd2472af6
--- /dev/null
+++ b/arch/riscv/include/asm/topology.h
@@ -0,0 +1,19 @@
+/* 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
+#define arch_update_cpu_topology topology_update_cpu_topology
+
+
+#include <asm-generic/topology.h>
+#endif /* __ASM_RISCV_TOPOLOGY_H */
-- 
2.20.1

Re: [RFC PATCH] riscv: export cpu/freq invariant to scheduler

[Andrew Jones]

On Wed, Mar 22, 2023 at 02:18:56PM +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@gmail.com>
> ---
>  arch/riscv/include/asm/topology.h | 19 +++++++++++++++++++
>  1 file changed, 19 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..14bbd2472af6
> --- /dev/null
> +++ b/arch/riscv/include/asm/topology.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_RISCV_TOPOLOGY_H
> +#define __ASM_RISCV_TOPOLOGY_H

riscv uses a single leading underscore.

> +
> +#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
> +#define arch_update_cpu_topology topology_update_cpu_topology
> +
> +
> +#include <asm-generic/topology.h>
> +#endif /* __ASM_RISCV_TOPOLOGY_H */
> -- 
> 2.20.1
>

This looks reasonable, at least from a "do what arm64 does" type of
perspective. Why the RFC? Is it not tested?

Also, if you repost, could please neaten it up a bit? Aligning all
the defines would help and removing the extra blank line. Finally,
why wasn't the "/* Enable topology flag updates */" comment also
lifted from arm64 like the others?

Thanks,
drew

Re: [RFC PATCH] riscv: export cpu/freq invariant to scheduler

[Song Shuai]

Andrew Jones <ajones@ventanamicro.com> 于2023年3月22日周三 08:03写道：
>
> On Wed, Mar 22, 2023 at 02:18:56PM +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@gmail.com>
> > ---
> >  arch/riscv/include/asm/topology.h | 19 +++++++++++++++++++
> >  1 file changed, 19 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..14bbd2472af6
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/topology.h
> > @@ -0,0 +1,19 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __ASM_RISCV_TOPOLOGY_H
> > +#define __ASM_RISCV_TOPOLOGY_H
>
> riscv uses a single leading underscore.
ok.
>
> > +
> > +#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
> > +#define arch_update_cpu_topology topology_update_cpu_topology
> > +
> > +
> > +#include <asm-generic/topology.h>
> > +#endif /* __ASM_RISCV_TOPOLOGY_H */
> > --
> > 2.20.1
> >
>
> This looks reasonable, at least from a "do what arm64 does" type of
> perspective. Why the RFC? Is it not tested?
I only tested it in the qemu sifive_u machine with a customed dtb
not sure if it works in real hardware, so I posted it with RFC.
>
> Also, if you repost, could please neaten it up a bit? Aligning all
> the defines would help and removing the extra blank line. Finally,
> why wasn't the "/* Enable topology flag updates */" comment also
> lifted from arm64 like the others?
I'll add the comment back and tidy it up in the next post.
>
> Thanks,
> drew



-- 
Thanks,
Song