Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967289Ab3DRRYB (ORCPT ); Thu, 18 Apr 2013 13:24:01 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:48620 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967125Ab3DRRX5 (ORCPT ); Thu, 18 Apr 2013 13:23:57 -0400 From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Kevin Hilman , Li Zhong , Oleg Nesterov , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner Subject: [PATCH 1/3] nohz: New APIs to re-evaluate the tick on full dynticks CPUs Date: Thu, 18 Apr 2013 19:23:40 +0200 Message-Id: <1366305822-5499-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1366305822-5499-1-git-send-email-fweisbec@gmail.com> References: <1366305822-5499-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4037 Lines: 129 Provide two new helpers in order to notify the full dynticks CPUs about some internal system changes against which they may reconsider the state of their tick. Some practical examples include: posix cpu timers, perf tick and sched clock tick. For now the notifying handler, implemented through IPIs, is a stub that will be implemented when we get the tick stop/restart infrastructure in. Signed-off-by: Frederic Weisbecker Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Li Zhong Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- include/linux/tick.h | 4 +++ kernel/time/Kconfig | 1 + kernel/time/tick-sched.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 56 insertions(+), 0 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index b4e3b0c..c2dcfb1 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -159,8 +159,12 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; } #ifdef CONFIG_NO_HZ_FULL extern int tick_nohz_full_cpu(int cpu); +extern void tick_nohz_full_kick(void); +extern void tick_nohz_full_kick_all(void); #else static inline int tick_nohz_full_cpu(int cpu) { return 0; } +static inline void tick_nohz_full_kick(void) { } +static inline void tick_nohz_full_kick_all(void) { } #endif diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 358d601..fbb4c7e 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -111,6 +111,7 @@ config NO_HZ_FULL select RCU_USER_QS select RCU_NOCB_CPU select CONTEXT_TRACKING_FORCE + select IRQ_WORK help Adaptively try to shutdown the tick whenever possible, even when the CPU is running tasks. Typically this requires running a single diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 369b576..2bcad5b 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -147,6 +147,57 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) static cpumask_var_t nohz_full_mask; bool have_nohz_full_mask; +/* + * Re-evaluate the need for the tick on the current CPU + * and restart it if necessary. + */ +static void tick_nohz_full_check(void) +{ + /* + * STUB for now, will be filled with the full tick stop/restart + * infrastructure patches + */ +} + +static void nohz_full_kick_work_func(struct irq_work *work) +{ + tick_nohz_full_check(); +} + +static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { + .func = nohz_full_kick_work_func, +}; + +/* + * Kick the current CPU if it's full dynticks in order to force it to + * re-evaluate its dependency on the tick and restart it if necessary. + */ +void tick_nohz_full_kick(void) +{ + if (tick_nohz_full_cpu(smp_processor_id())) + irq_work_queue(&__get_cpu_var(nohz_full_kick_work)); +} + +static void nohz_full_kick_ipi(void *info) +{ + tick_nohz_full_check(); +} + +/* + * Kick all full dynticks CPUs in order to force these to re-evaluate + * their dependency on the tick and restart it if necessary. + */ +void tick_nohz_full_kick_all(void) +{ + if (!have_nohz_full_mask) + return; + + preempt_disable(); + smp_call_function_many(nohz_full_mask, + nohz_full_kick_ipi, NULL, false); + preempt_enable(); +} + int tick_nohz_full_cpu(int cpu) { if (!have_nohz_full_mask) -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/