Messages in this thread Patch in this message |  | | Date | Tue, 16 Jan 2024 15:10:26 +0800 | | Subject | Re: [PATCH] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512 | | From | Kefeng Wang <> |
| |
On 2024/1/15 23:39, Russell King (Oracle) wrote: > On Thu, Dec 14, 2023 at 04:05:56PM -0800, Christoph Lameter (Ampere) wrote: >> Index: linux/arch/arm64/Kconfig >> =================================================================== >> --- linux.orig/arch/arm64/Kconfig >> +++ linux/arch/arm64/Kconfig >> @@ -1407,7 +1407,21 @@ config SCHED_SMT >> config NR_CPUS >> int "Maximum number of CPUs (2-4096)" >> range 2 4096 > > I think your mailer got to your patch and messed up the white space. > There are two spaces before each of these lines rather than the usual > one. > >> - default "256" >> + default 512 >> + >> +# >> +# Determines the placement of cpumasks. >> +# >> +# With CPUMASK_OFFSTACK the cpumasks are dynamically allocated. >> +# Useful for machines with lots of core because it avoids increasing >> +# the size of many of the data structures in the kernel. >> +# >> +# If this is off then the cpumasks have a static sizes and are >> +# embedded within data structures. >> +# >> +config CPUMASK_OFFSTACK >> + def_bool y >> + depends on NR_CPUS > 256 > > Should that be ">= 256" ?
Maybe just select CPUMASK_OFFSTACK if NR_CPUS >= 256,
But could we just make CPUMASK_OFFSTACK configurable and let user/distro to enable it?
diff --git a/lib/Kconfig b/lib/Kconfig index 5ddda7c2ed9b..4254be5aa843 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -535,7 +535,9 @@ config CHECK_SIGNATURE bool
config CPUMASK_OFFSTACK - bool "Force CPU masks off stack" if DEBUG_PER_CPU_MAPS + bool "Force CPU masks off stack" + depends on SMP + default n help Use dynamic allocation for cpumask_var_t, instead of putting them on the stack. This is a bit more expensive, but avoids
> >> >> config HOTPLUG_CPU >> bool "Support for hot-pluggable CPUs" > > Same here. >
|  |