linux-kernel - Re: [PATCH v7 4/8] powerpc/smp: Introduce CONFIG_SCHED

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Message-ID: <20251014141730.GZ3245006@noisy.programming.kicks-ass.net>
Date: Tue, 14 Oct 2025 16:17:30 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	K Prateek Nayak <kprateek.nayak@....com>,
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	Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: Re: [PATCH v7 4/8] powerpc/smp: Introduce CONFIG_SCHED_MC to guard
 MC scheduling bits

On Tue, Oct 14, 2025 at 02:37:11PM +0200, Geert Uytterhoeven wrote:

> > > > +       help
> > > > +         Improves the CPU scheduler's decision making when dealing with
> > > > +         MultiThreading at a cost of slightly increased overhead in some
> > > > +         places. If unsure say N here.
> > >
> > > So it should default to n?
> >
> > That's just help text that got carried around. Many of the architectures
> > that had default y still had this text on. I suppose we can change it if
> > someone cares.
> 
> Please do so.

How about we remove the recommendation like so? There are many help
things that do not have a recommendation. Mostly these options add a
little code and the most expensive bits tend to be gated by
static_branch() so it really shouldn't be that bit of a burden.

CONFIG_SMP was the big one for the scheduler, and Ingo recently removed
that (he did an effective unifdef CONFIG_SMP=y on the scheduler code).

---
diff --git a/arch/Kconfig b/arch/Kconfig
index ebe08b9186ad..3d8e2025a4ac 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -57,7 +57,7 @@ config SCHED_SMT
 	help
 	  Improves the CPU scheduler's decision making when dealing with
 	  MultiThreading at a cost of slightly increased overhead in some
-	  places. If unsure say N here.
+	  places.
 
 config SCHED_CLUSTER
 	bool "Cluster scheduler support"
@@ -77,7 +77,7 @@ config SCHED_MC
 	help
 	  Multi-core scheduler support improves the CPU scheduler's decision
 	  making when dealing with multi-core CPU chips at a cost of slightly
-	  increased overhead in some places. If unsure say N here.
+	  increased overhead in some places.
 
 # Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
 config HOTPLUG_CORE_SYNC