Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Thu, 16 May 2019 16:55:33 +0100 | Subject | [PATCH 3.16 41/86] x86/Kconfig: Select SCHED_SMT if SMP enabled |
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3.16.68-rc1 review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner <tglx@linutronix.de>
commit dbe733642e01dd108f71436aaea7b328cb28fd87 upstream.
CONFIG_SCHED_SMT is enabled by all distros, so there is not a real point to have it configurable. The runtime overhead in the core scheduler code is minimal because the actual SMT scheduling parts are conditional on a static key.
This allows to expose the scheduler's SMT state static key to the speculation control code. Alternatively the scheduler's static key could be made always available when CONFIG_SMP is enabled, but that's just adding an unused static key to every other architecture for nothing.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Casey Schaufler <casey.schaufler@intel.com> Cc: Asit Mallick <asit.k.mallick@intel.com> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Jon Masters <jcm@redhat.com> Cc: Waiman Long <longman9394@gmail.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Dave Stewart <david.c.stewart@intel.com> Cc: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20181125185004.337452245@linutronix.de [bwh: Backported to 3.16: CONFIG_SCHED_SMT depended on CONFG_X86_HT, but that also follows CONFIG_SMP] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- arch/x86/Kconfig | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)
--- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -798,13 +798,7 @@ config NR_CPUS approximately eight kilobytes to the kernel image. config SCHED_SMT - bool "SMT (Hyperthreading) scheduler support" - depends on X86_HT - ---help--- - SMT scheduler support improves the CPU scheduler's decision making - when dealing with Intel Pentium 4 chips with HyperThreading at a - cost of slightly increased overhead in some places. If unsure say - N here. + def_bool y if SMP config SCHED_MC def_bool y
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