From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7021DC433F5 for ; Tue, 14 Sep 2021 10:31:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 599EE60EB6 for ; Tue, 14 Sep 2021 10:31:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232037AbhINKdM (ORCPT ); Tue, 14 Sep 2021 06:33:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:56934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231825AbhINKc7 (ORCPT ); Tue, 14 Sep 2021 06:32:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6DE5860EB6; Tue, 14 Sep 2021 10:31:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631615502; bh=Xz97ndFvtoN5aTFQEIhbJ9GJFnnXiIXoH/Esjb46dpM=; h=From:To:Cc:Subject:Date:From; b=JBw95VoavzLQLCWLZ5ePpVxRX2b6lcmcdIduG6QtNlQTB2JmO98PaUizwEz022CE0 R772T05S804wJlCcJ6SINkEGeGUD1pRVc6l9opfZXOcqGpwrxN9IBp8QA/VI0/5h2U LyKHSGN1didtA3B1mfLXWLKXBDDYZYrO84qA7DTeYC+bqKANqp+PGXYr+SCj4UQrVM CHec75X4bJLH08vjoZXjfFouCtQkO9sz1xelEFBI2vR6RYVhrigtDKBZeS7Kk+pB9o dBqs+J7SkZ4P4+u8/Dk2QN+EEZs552+HXDMsW02Lln/cZyJi69IB2awd6gNQKZGJx8 ac9A/j60zcs5w== From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Frederic Weisbecker , Ingo Molnar Subject: [PATCH v3] sched: Provide Kconfig support for default dynamic preempt mode Date: Tue, 14 Sep 2021 12:31:34 +0200 Message-Id: <20210914103134.11309-1-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently the boot defined preempt behaviour (aka dynamic preempt) selects full preemption by default when the "preempt=" boot parameter is omitted. However distros may rather want to default to either no preemption or voluntary preemption. To provide with this flexibility, make dynamic preemption a visible Kconfig option and adapt the preemption behaviour selected by the user to either static or dynamic preemption. Signed-off-by: Frederic Weisbecker --- kernel/Kconfig.preempt | 32 +++++++++++++++++++++++--------- kernel/sched/core.c | 29 ++++++++++++++++++++++++++--- 2 files changed, 49 insertions(+), 12 deletions(-) diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 5876e30c5740..60f1bfc3c7b2 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -2,10 +2,11 @@ choice prompt "Preemption Model" - default PREEMPT_NONE + default PREEMPT_NONE_BEHAVIOUR -config PREEMPT_NONE +config PREEMPT_NONE_BEHAVIOUR bool "No Forced Preemption (Server)" + select PREEMPT_NONE if !PREEMPT_DYNAMIC help This is the traditional Linux preemption model, geared towards throughput. It will still provide good latencies most of the @@ -17,9 +18,10 @@ config PREEMPT_NONE raw processing power of the kernel, irrespective of scheduling latencies. -config PREEMPT_VOLUNTARY +config PREEMPT_VOLUNTARY_BEHAVIOUR bool "Voluntary Kernel Preemption (Desktop)" depends on !ARCH_NO_PREEMPT + select PREEMPT_VOLUNTARY if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by adding more "explicit preemption points" to the kernel code. These new @@ -35,12 +37,10 @@ config PREEMPT_VOLUNTARY Select this if you are building a kernel for a desktop system. -config PREEMPT +config PREEMPT_BEHAVIOUR bool "Preemptible Kernel (Low-Latency Desktop)" depends on !ARCH_NO_PREEMPT - select PREEMPTION - select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK - select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC + select PREEMPT help This option reduces the latency of the kernel by making all kernel code (that is not executing in a critical section) @@ -58,7 +58,7 @@ config PREEMPT config PREEMPT_RT bool "Fully Preemptible Kernel (Real-Time)" - depends on EXPERT && ARCH_SUPPORTS_RT + depends on EXPERT && ARCH_SUPPORTS_RT && !PREEMPT_DYNAMIC select PREEMPTION help This option turns the kernel into a real-time kernel by replacing @@ -75,6 +75,17 @@ config PREEMPT_RT endchoice +config PREEMPT_NONE + bool + +config PREEMPT_VOLUNTARY + bool + +config PREEMPT + bool + select PREEMPTION + select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK + config PREEMPT_COUNT bool @@ -83,7 +94,10 @@ config PREEMPTION select PREEMPT_COUNT config PREEMPT_DYNAMIC - bool + bool "Preemption behaviour defined on boot" + depends on HAVE_PREEMPT_DYNAMIC + select PREEMPT + default y help This option allows to define the preemption model on the kernel command line parameter and thus override the default preemption diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1bba4128a3e6..af2ca7ea7dda 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6586,12 +6586,13 @@ EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace); */ enum { - preempt_dynamic_none = 0, + preempt_dynamic_undefined = -1, + preempt_dynamic_none, preempt_dynamic_voluntary, preempt_dynamic_full, }; -int preempt_dynamic_mode = preempt_dynamic_full; +int preempt_dynamic_mode = preempt_dynamic_undefined; int sched_dynamic_mode(const char *str) { @@ -6664,7 +6665,27 @@ static int __init setup_preempt_mode(char *str) } __setup("preempt=", setup_preempt_mode); -#endif /* CONFIG_PREEMPT_DYNAMIC */ +static void __init preempt_dynamic_init(void) +{ + if (preempt_dynamic_mode == preempt_dynamic_undefined) { + if (IS_ENABLED(CONFIG_PREEMPT_NONE_BEHAVIOUR)) { + sched_dynamic_update(preempt_dynamic_none); + } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY_BEHAVIOUR)) { + sched_dynamic_update(preempt_dynamic_voluntary); + } else { + /* Default static call setting, nothing to do */ + WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_BEHAVIOUR)); + preempt_dynamic_mode = preempt_dynamic_full; + pr_info("Dynamic Preempt: full\n"); + } + } +} + +#else /* !CONFIG_PREEMPT_DYNAMIC */ + +static inline void preempt_dynamic_init(void) { } + +#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */ /* * This is the entry point to schedule() from kernel preemption @@ -9464,6 +9485,8 @@ void __init sched_init(void) init_uclamp(); + preempt_dynamic_init(); + scheduler_running = 1; } -- 2.25.1