ACK/Cmnt: [SRU][K/Unstable][PATCH 0/1] Support up to 32 CPUs on riscv64

[Emil Renner Berthing]

On Wed, 31 Aug 2022 at 15:26, Tim Gardner <tim.gardner at canonical.com> wrote:
>
> On 8/31/22 06:24, Emil Renner Berthing wrote:
> > [Impact]
> >
> >   * Currently our riscv64 kernels don't support more than 8 CPUs.
> >
> >   * The QEMU 7.0 virt machine supports up to 512 virtual CPUs.
> >
> >   * Raising CONFIG_NR_CPUS to the maximum of 32 allows us to use
> >     more of them.
> >
> > [Test Plan]
> >
> >   * Run riscv64 Ubuntu in a QEMU virt instance with more than 8
> >     virtual CPUs and see that only 8 of them are used.
> >
> >   * After raising CONFIG_NR_CPUS up to 32 of them should be used.
> >
> > [Where problems could occur]
> >
> >   * This will allocate slightly more RAM which might hurt very small
> >     machines.
> >
> > Emil Renner Berthing (1):
> >    UBUNTU: [Config] Raise riscv64 CONFIG_NR_CPUS to 32
> >
> >   debian.master/config/annotations                   | 2 +-
> >   debian.master/config/riscv64/config.common.riscv64 | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> Acked-by: Tim Gardner <tim.gardner at canonical.com>
>
> Have you profiled memory usage to see how much more 512 would use ?

No, because for now arch/riscv/Kconfig specifies "range 2 32" for
CONFIG_NR_CPUS, so 32 is the maximum it allows until something like
this patch is accepted:
https://lore.kernel.org/all/20220420112408.155561-1-apatel@ventanamicro.com/

/Emil

/Emil

> --
> -----------
> Tim Gardner
> Canonical, Inc