From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752050Ab2LTSdu (ORCPT ); Thu, 20 Dec 2012 13:33:50 -0500 Received: from mail-wg0-f42.google.com ([74.125.82.42]:62314 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751947Ab2LTSdh (ORCPT ); Thu, 20 Dec 2012 13:33:37 -0500 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Ingo Molnar , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner Subject: [PATCH 06/24] nohz: Basic full dynticks interface Date: Thu, 20 Dec 2012 19:32:53 +0100 Message-Id: <1356028391-14427-7-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1356028391-14427-1-git-send-email-fweisbec@gmail.com> References: <1356028391-14427-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Start with a very simple interface to define full dynticks CPU: use a boot time option defined cpumask through the "full_nohz=" kernel parameter. Make sure you keep at least one CPU outside this range to handle the timekeeping. Also full_nohz= must match rcu_nocb= value. Suggested-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- include/linux/tick.h | 7 +++++++ kernel/time/Kconfig | 9 +++++++++ kernel/time/tick-sched.c | 23 +++++++++++++++++++++++ 3 files changed, 39 insertions(+), 0 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index 553272e..2d4f6f0 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -157,6 +157,13 @@ static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; } static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; } # endif /* !NO_HZ */ +#ifdef CONFIG_NO_HZ_FULL +int tick_nohz_full_cpu(int cpu); +#else +static inline int tick_nohz_full_cpu(int cpu) { return 0; } +#endif + + # ifdef CONFIG_CPU_IDLE_GOV_MENU extern void menu_hrtimer_cancel(void); # else diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 8601f0d..0a1bc72 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -70,6 +70,15 @@ config NO_HZ only trigger on an as-needed basis both when the system is busy and when the system is idle. +config NO_HZ_FULL + bool "Full tickless system" + depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN && RCU_NOCB_CPU + select CONTEXT_TRACKING_FORCE + help + Try to be tickless everywhere, not just in idle. (You need + to fill up the full_nohz_mask boot parameter). + + config HIGH_RES_TIMERS bool "High Resolution Timer Support" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index ad0e6fa..fac9ba4 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -142,6 +142,29 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) profile_tick(CPU_PROFILING); } +#ifdef CONFIG_NO_HZ_FULL +static cpumask_var_t full_nohz_mask; +bool have_full_nohz_mask; + +int tick_nohz_full_cpu(int cpu) +{ + if (!have_full_nohz_mask) + return 0; + + return cpumask_test_cpu(cpu, full_nohz_mask); +} + +/* Parse the boot-time nohz CPU list from the kernel parameters. */ +static int __init tick_nohz_full_setup(char *str) +{ + alloc_bootmem_cpumask_var(&full_nohz_mask); + have_full_nohz_mask = true; + cpulist_parse(str, full_nohz_mask); + return 1; +} +__setup("full_nohz=", tick_nohz_full_setup); +#endif + /* * NOHZ - aka dynamic tick functionality */ -- 1.7.5.4