The powernv platform supports Power7 and later CPUs, all of which are
multithreaded and multicore.
As such we never build a SMP=n kernel for those machines, other than
possibly for debugging or running in a simulator.
In the debugging case we can get a similar effect by booting with
nr_cpus=1, or there's always the option of building a custom kernel with
SMP hacked out.
For running in simulators the code size reduction from building without
SMP is not particularly important, what matters is the number of
instructions executed. A quick test shows that a SMP=y kernel takes ~6%
more instructions to boot to a shell. Booting with nr_cpus=1 recovers
about half that deficit.
On the flip side, keeping the SMP=n kernel building can be a pain at
times. And although we've mostly kept it building in recent years, no
one is regularly testing that the SMP=n kernel actually boots and works
well on these machines.
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/platforms/powernv/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/platforms/powernv/Kconfig
b/arch/powerpc/platforms/powernv/Kconfig
index 3a07e4dcf97c..bd8d41d3a1b3 100644
--- a/arch/powerpc/platforms/powernv/Kconfig
+++ b/arch/powerpc/platforms/powernv/Kconfig
@@ -19,6 +19,7 @@ config PPC_POWERNV
select CPU_FREQ_GOV_ONDEMAND
select CPU_FREQ_GOV_CONSERVATIVE
select PPC_DOORBELL
+ select FORCE_SMP
default y
config OPAL_PRD
--
2.7.4
