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.
