linux-kernel - [RFC PATCH v2 5/5] kernel: drop PREEMPT

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Date:   Fri,  9 Oct 2020 14:29:26 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Mel Gorman <mgorman@...e.de>,
        Frederic Weisbecker <fweisbecker@...e.de>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [RFC PATCH v2 5/5] kernel: drop PREEMPT_NONE compile time option

From: Michal Hocko <mhocko@...e.com>

Now that preempt_mode command line parameter supports both preempt_none
and preempt_voluntary we do not necessarily need a config option for
this preemption mode and we can reduce the overall config space a bit.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 kernel/Kconfig.preempt | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index e142f36dd429..e19b7d3a8d3c 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -2,23 +2,10 @@
 
 choice
 	prompt "Preemption Model"
-	default PREEMPT_NONE
-
-config PREEMPT_NONE
-	bool "No Forced Preemption (Server)"
-	help
-	  This is the traditional Linux preemption model, geared towards
-	  throughput. It will still provide good latencies most of the
-	  time, but there are no guarantees and occasional longer delays
-	  are possible.
-
-	  Select this option if you are building a kernel for a server or
-	  scientific/computation system, or if you want to maximize the
-	  raw processing power of the kernel, irrespective of scheduling
-	  latencies.
+	default PREEMPT_VOLUNTARY
 
 config PREEMPT_VOLUNTARY
-	bool "Voluntary Kernel Preemption (Desktop)"
+	bool "Voluntary Kernel Preemption (Throughput oriented workloads)"
 	help
 	  This option reduces the latency of the kernel by adding more
 	  "explicit preemption points" to the kernel code. These new
@@ -35,7 +22,7 @@ config PREEMPT_VOLUNTARY
 	  Select this if you are building a kernel for a desktop system.
 
 config PREEMPT
-	bool "Preemptible Kernel (Low-Latency Desktop)"
+	bool "Preemptible Kernel (Low-Latency oriented workloads)"
 	depends on !ARCH_NO_PREEMPT
 	select PREEMPTION
 	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
@@ -75,7 +62,7 @@ endchoice
 
 config PREEMPT_DYNAMIC
 	bool "Allow boot time preemption model selection"
-	depends on PREEMPT_NONE || PREEMPT_VOLUNTARY
+	depends on PREEMPT_VOLUNTARY
 	help
 	  This option allows to define the preemption model on the kernel
 	  command line parameter and thus override the default preemption
-- 
2.28.0