Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756698AbZKEG6X (ORCPT ); Thu, 5 Nov 2009 01:58:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756491AbZKEG6V (ORCPT ); Thu, 5 Nov 2009 01:58:21 -0500 Received: from hera.kernel.org ([140.211.167.34]:60806 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756593AbZKEG6K (ORCPT ); Thu, 5 Nov 2009 01:58:10 -0500 Date: Thu, 5 Nov 2009 06:57:55 GMT From: tip-bot for Martin Schwidefsky Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, schwidefsky@de.ibm.com, tglx@linutronix.de Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com, tglx@linutronix.de In-Reply-To: <20090929122533.402715150@de.ibm.com> References: <20090929122533.402715150@de.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/core] nohz: Introduce arch_needs_cpu Message-ID: Git-Commit-ID: 3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5134 Lines: 135 Commit-ID: 3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 Gitweb: http://git.kernel.org/tip/3c5d92a0cfb5103c0d5ab74d4ae6373d3af38148 Author: Martin Schwidefsky AuthorDate: Tue, 29 Sep 2009 14:25:16 +0200 Committer: Thomas Gleixner CommitDate: Thu, 5 Nov 2009 07:53:53 +0100 nohz: Introduce arch_needs_cpu Allow the architecture to request a normal jiffy tick when the system goes idle and tick_nohz_stop_sched_tick is called . On s390 the hook is used to prevent the system going fully idle if there has been an interrupt other than a clock comparator interrupt since the last wakeup. On s390 the HiperSockets response time for 1 connection ping-pong goes down from 42 to 34 microseconds. The CPU cost decreases by 27%. Signed-off-by: Martin Schwidefsky LKML-Reference: <20090929122533.402715150@de.ibm.com> Signed-off-by: Thomas Gleixner --- arch/s390/include/asm/cputime.h | 8 ++++++++ arch/s390/kernel/s390_ext.c | 2 ++ arch/s390/kernel/vtime.c | 2 ++ drivers/s390/cio/cio.c | 1 + include/linux/tick.h | 3 +++ kernel/time/tick-sched.c | 13 ++++++++----- 6 files changed, 24 insertions(+), 5 deletions(-) diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h index 24b1244..95f3561 100644 --- a/arch/s390/include/asm/cputime.h +++ b/arch/s390/include/asm/cputime.h @@ -183,6 +183,7 @@ struct s390_idle_data { unsigned long long idle_count; unsigned long long idle_enter; unsigned long long idle_time; + int nohz_delay; }; DECLARE_PER_CPU(struct s390_idle_data, s390_idle); @@ -198,4 +199,11 @@ static inline void s390_idle_check(void) vtime_start_cpu(); } +static inline int s390_nohz_delay(int cpu) +{ + return per_cpu(s390_idle, cpu).nohz_delay != 0; +} + +#define arch_needs_cpu(cpu) s390_nohz_delay(cpu) + #endif /* _S390_CPUTIME_H */ diff --git a/arch/s390/kernel/s390_ext.c b/arch/s390/kernel/s390_ext.c index 0de305b..59618bc 100644 --- a/arch/s390/kernel/s390_ext.c +++ b/arch/s390/kernel/s390_ext.c @@ -126,6 +126,8 @@ void __irq_entry do_extint(struct pt_regs *regs, unsigned short code) /* Serve timer interrupts first. */ clock_comparator_work(); kstat_cpu(smp_processor_id()).irqs[EXTERNAL_INTERRUPT]++; + if (code != 0x1004) + __get_cpu_var(s390_idle).nohz_delay = 1; index = ext_hash(code); for (p = ext_int_hash[index]; p; p = p->next) { if (likely(p->code == code)) diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c index c41bb0d..b59a812 100644 --- a/arch/s390/kernel/vtime.c +++ b/arch/s390/kernel/vtime.c @@ -167,6 +167,8 @@ void vtime_stop_cpu(void) /* Wait for external, I/O or machine check interrupt. */ psw.mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_IO | PSW_MASK_EXT; + idle->nohz_delay = 0; + /* Check if the CPU timer needs to be reprogrammed. */ if (vq->do_spt) { __u64 vmax = VTIMER_MAX_SLICE; diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c index 138124f..126f240 100644 --- a/drivers/s390/cio/cio.c +++ b/drivers/s390/cio/cio.c @@ -618,6 +618,7 @@ void __irq_entry do_IRQ(struct pt_regs *regs) old_regs = set_irq_regs(regs); s390_idle_check(); irq_enter(); + __get_cpu_var(s390_idle).nohz_delay = 1; if (S390_lowcore.int_clock >= S390_lowcore.clock_comparator) /* Serve timer interrupts first. */ clock_comparator_work(); diff --git a/include/linux/tick.h b/include/linux/tick.h index 0482229..8dc0821 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -98,6 +98,9 @@ extern int tick_check_oneshot_change(int allow_nohz); extern struct tick_sched *tick_get_tick_sched(int cpu); extern void tick_check_idle(int cpu); extern int tick_oneshot_mode_active(void); +# ifndef arch_needs_cpu +# define arch_needs_cpu(cpu) (0) +# endif # else static inline void tick_clock_notify(void) { } static inline int tick_check_oneshot_change(int allow_nohz) { return 0; } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 7378e2c..3840f6d 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -264,12 +264,15 @@ void tick_nohz_stop_sched_tick(int inidle) last_jiffies = jiffies; } while (read_seqretry(&xtime_lock, seq)); - /* Get the next timer wheel timer */ - next_jiffies = get_next_timer_interrupt(last_jiffies); - delta_jiffies = next_jiffies - last_jiffies; - - if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu)) + if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || + arch_needs_cpu(cpu)) { + next_jiffies = last_jiffies + 1; delta_jiffies = 1; + } else { + /* Get the next timer wheel timer */ + next_jiffies = get_next_timer_interrupt(last_jiffies); + delta_jiffies = next_jiffies - last_jiffies; + } /* * Do not stop the tick, if we are only one off * or if the cpu is required for rcu -- 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/