linux-kernel - Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE, PREEMPT

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Message-ID: <20201009101044.GH4967@dhcp22.suse.cz>
Date:   Fri, 9 Oct 2020 12:10:44 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbecker@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE,
 PREEMPT_VOLUNTARY on kernel command line

On Fri 09-10-20 11:42:45, Peter Zijlstra wrote:
> On Fri, Oct 09, 2020 at 11:12:18AM +0200, Michal Hocko wrote:
> > Is there any additional feedback? Should I split up the patch and repost
> > for inclusion?
> 
> Maybe remove PREEMPT_NONE after that?  Since that's then equivalent to
> building with VOLUNTARY and booting with preempt=none.

So do you mean that I should post an additional patch which does this on
top? With a justification that there is one option less to chose from?

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index bf82259cff96..103a5f9e4bcf 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -2,20 +2,7 @@
 
 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)"

-- 
Michal Hocko
SUSE Labs