Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760440AbYHDG0T (ORCPT ); Mon, 4 Aug 2008 02:26:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754800AbYHDG0L (ORCPT ); Mon, 4 Aug 2008 02:26:11 -0400 Received: from viefep18-int.chello.at ([213.46.255.22]:3002 "EHLO viefep18-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754717AbYHDG0J (ORCPT ); Mon, 4 Aug 2008 02:26:09 -0400 X-SourceIP: 80.57.229.25 Subject: Re: VolanoMark regression with 2.6.27-rc1 From: Peter Zijlstra To: Dhaval Giani Cc: "Zhang, Yanmin" , Ingo Molnar , LKML , Srivatsa Vaddagiri , Aneesh Kumar KV , Balbir Singh In-Reply-To: <20080804055339.GB5444@linux.vnet.ibm.com> References: <1217474425.25608.150.camel@ymzhang> <1217489463.25608.157.camel@ymzhang> <1217489949.8157.78.camel@twins> <1217490560.25608.168.camel@ymzhang> <1217551154.25608.169.camel@ymzhang> <20080801051407.GA5232@linux.vnet.ibm.com> <1217826278.25608.198.camel@ymzhang> <20080804052228.GA5444@linux.vnet.ibm.com> <1217828278.25608.206.camel@ymzhang> <20080804055339.GB5444@linux.vnet.ibm.com> Content-Type: text/plain Date: Mon, 04 Aug 2008 08:26:07 +0200 Message-Id: <1217831167.9016.41.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10664 Lines: 402 On Mon, 2008-08-04 at 11:23 +0530, Dhaval Giani wrote: > Peter, vatsa, any ideas? --- Patches in tip/sched/clock --- diff --git a/include/linux/sched.h b/include/linux/sched.h index 5270d44..ea436bc 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1572,28 +1572,13 @@ static inline void sched_clock_idle_sleep_event(void) static inline void sched_clock_idle_wakeup_event(u64 delta_ns) { } - -#ifdef CONFIG_NO_HZ -static inline void sched_clock_tick_stop(int cpu) -{ -} - -static inline void sched_clock_tick_start(int cpu) -{ -} -#endif - -#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ +#else extern void sched_clock_init(void); extern u64 sched_clock_cpu(int cpu); extern void sched_clock_tick(void); extern void sched_clock_idle_sleep_event(void); extern void sched_clock_idle_wakeup_event(u64 delta_ns); -#ifdef CONFIG_NO_HZ -extern void sched_clock_tick_stop(int cpu); -extern void sched_clock_tick_start(int cpu); #endif -#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ /* * For kernel-internal use: high-speed (but slightly incorrect) per-cpu diff --git a/kernel/Kconfig.hz b/kernel/Kconfig.hz index 382dd5a..94fabd5 100644 --- a/kernel/Kconfig.hz +++ b/kernel/Kconfig.hz @@ -55,4 +55,4 @@ config HZ default 1000 if HZ_1000 config SCHED_HRTICK - def_bool HIGH_RES_TIMERS && USE_GENERIC_SMP_HELPERS + def_bool HIGH_RES_TIMERS && (!SMP || USE_GENERIC_SMP_HELPERS) diff --git a/kernel/sched.c b/kernel/sched.c index 21f7da9..9a76e92 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -834,7 +834,7 @@ static inline u64 global_rt_period(void) static inline u64 global_rt_runtime(void) { - if (sysctl_sched_rt_period < 0) + if (sysctl_sched_rt_runtime < 0) return RUNTIME_INF; return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC; diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index 22ed55d..074edc9 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -32,14 +32,18 @@ #include #include +/* + * Scheduler clock - returns current time in nanosec units. + * This is default implementation. + * Architectures and sub-architectures can override this. + */ +unsigned long long __attribute__((weak)) sched_clock(void) +{ + return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); +} #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK -#define MULTI_SHIFT 15 -/* Max is double, Min is 1/2 */ -#define MAX_MULTI (2LL << MULTI_SHIFT) -#define MIN_MULTI (1LL << (MULTI_SHIFT-1)) - struct sched_clock_data { /* * Raw spinlock - this is a special case: this might be called @@ -49,14 +53,9 @@ struct sched_clock_data { raw_spinlock_t lock; unsigned long tick_jiffies; - u64 prev_raw; u64 tick_raw; u64 tick_gtod; u64 clock; - s64 multi; -#ifdef CONFIG_NO_HZ - int check_max; -#endif }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data); @@ -84,90 +83,39 @@ void sched_clock_init(void) scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; scd->tick_jiffies = now_jiffies; - scd->prev_raw = 0; scd->tick_raw = 0; scd->tick_gtod = ktime_now; scd->clock = ktime_now; - scd->multi = 1 << MULTI_SHIFT; -#ifdef CONFIG_NO_HZ - scd->check_max = 1; -#endif } sched_clock_running = 1; } -#ifdef CONFIG_NO_HZ -/* - * The dynamic ticks makes the delta jiffies inaccurate. This - * prevents us from checking the maximum time update. - * Disable the maximum check during stopped ticks. - */ -void sched_clock_tick_stop(int cpu) -{ - struct sched_clock_data *scd = cpu_sdc(cpu); - - scd->check_max = 0; -} - -void sched_clock_tick_start(int cpu) -{ - struct sched_clock_data *scd = cpu_sdc(cpu); - - scd->check_max = 1; -} - -static int check_max(struct sched_clock_data *scd) -{ - return scd->check_max; -} -#else -static int check_max(struct sched_clock_data *scd) -{ - return 1; -} -#endif /* CONFIG_NO_HZ */ - /* * update the percpu scd from the raw @now value * * - filter out backward motion * - use jiffies to generate a min,max window to clip the raw values */ -static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *time) +static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now) { unsigned long now_jiffies = jiffies; long delta_jiffies = now_jiffies - scd->tick_jiffies; u64 clock = scd->clock; u64 min_clock, max_clock; - s64 delta = now - scd->prev_raw; + s64 delta = now - scd->tick_raw; WARN_ON_ONCE(!irqs_disabled()); - - /* - * At schedule tick the clock can be just under the gtod. We don't - * want to push it too prematurely. - */ - min_clock = scd->tick_gtod + (delta_jiffies * TICK_NSEC); - if (min_clock > TICK_NSEC) - min_clock -= TICK_NSEC / 2; + min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC; if (unlikely(delta < 0)) { clock++; goto out; } - /* - * The clock must stay within a jiffie of the gtod. - * But since we may be at the start of a jiffy or the end of one - * we add another jiffy buffer. - */ - max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC; - - delta *= scd->multi; - delta >>= MULTI_SHIFT; + max_clock = min_clock + TICK_NSEC; - if (unlikely(clock + delta > max_clock) && check_max(scd)) { + if (unlikely(clock + delta > max_clock)) { if (clock < max_clock) clock = max_clock; else @@ -180,12 +128,10 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *tim if (unlikely(clock < min_clock)) clock = min_clock; - if (time) - *time = clock; - else { - scd->prev_raw = now; - scd->clock = clock; - } + scd->tick_jiffies = now_jiffies; + scd->clock = clock; + + return clock; } static void lock_double_clock(struct sched_clock_data *data1, @@ -203,7 +149,7 @@ static void lock_double_clock(struct sched_clock_data *data1, u64 sched_clock_cpu(int cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); - u64 now, clock; + u64 now, clock, this_clock, remote_clock; if (unlikely(!sched_clock_running)) return 0ull; @@ -212,43 +158,44 @@ u64 sched_clock_cpu(int cpu) now = sched_clock(); if (cpu != raw_smp_processor_id()) { - /* - * in order to update a remote cpu's clock based on our - * unstable raw time rebase it against: - * tick_raw (offset between raw counters) - * tick_gotd (tick offset between cpus) - */ struct sched_clock_data *my_scd = this_scd(); lock_double_clock(scd, my_scd); - now -= my_scd->tick_raw; - now += scd->tick_raw; + this_clock = __update_sched_clock(my_scd, now); + remote_clock = scd->clock; - now += my_scd->tick_gtod; - now -= scd->tick_gtod; + /* + * Use the opportunity that we have both locks + * taken to couple the two clocks: we take the + * larger time as the latest time for both + * runqueues. (this creates monotonic movement) + */ + if (likely(remote_clock < this_clock)) { + clock = this_clock; + scd->clock = clock; + } else { + /* + * Should be rare, but possible: + */ + clock = remote_clock; + my_scd->clock = remote_clock; + } __raw_spin_unlock(&my_scd->lock); - - __update_sched_clock(scd, now, &clock); - - __raw_spin_unlock(&scd->lock); - } else { __raw_spin_lock(&scd->lock); - __update_sched_clock(scd, now, NULL); - clock = scd->clock; - __raw_spin_unlock(&scd->lock); + clock = __update_sched_clock(scd, now); } + __raw_spin_unlock(&scd->lock); + return clock; } void sched_clock_tick(void) { struct sched_clock_data *scd = this_scd(); - unsigned long now_jiffies = jiffies; - s64 mult, delta_gtod, delta_raw; u64 now, now_gtod; if (unlikely(!sched_clock_running)) @@ -260,29 +207,14 @@ void sched_clock_tick(void) now = sched_clock(); __raw_spin_lock(&scd->lock); - __update_sched_clock(scd, now, NULL); + __update_sched_clock(scd, now); /* * update tick_gtod after __update_sched_clock() because that will * already observe 1 new jiffy; adding a new tick_gtod to that would * increase the clock 2 jiffies. */ - delta_gtod = now_gtod - scd->tick_gtod; - delta_raw = now - scd->tick_raw; - - if ((long)delta_raw > 0) { - mult = delta_gtod << MULTI_SHIFT; - do_div(mult, delta_raw); - scd->multi = mult; - if (scd->multi > MAX_MULTI) - scd->multi = MAX_MULTI; - else if (scd->multi < MIN_MULTI) - scd->multi = MIN_MULTI; - } else - scd->multi = 1 << MULTI_SHIFT; - scd->tick_raw = now; scd->tick_gtod = now_gtod; - scd->tick_jiffies = now_jiffies; __raw_spin_unlock(&scd->lock); } @@ -301,7 +233,6 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); void sched_clock_idle_wakeup_event(u64 delta_ns) { struct sched_clock_data *scd = this_scd(); - u64 now = sched_clock(); /* * Override the previous timestamp and ignore all @@ -310,9 +241,7 @@ void sched_clock_idle_wakeup_event(u64 delta_ns) * rq clock: */ __raw_spin_lock(&scd->lock); - scd->prev_raw = now; scd->clock += delta_ns; - scd->multi = 1 << MULTI_SHIFT; __raw_spin_unlock(&scd->lock); touch_softlockup_watchdog(); @@ -321,16 +250,6 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); #endif -/* - * Scheduler clock - returns current time in nanosec units. - * This is default implementation. - * Architectures and sub-architectures can override this. - */ -unsigned long long __attribute__((weak)) sched_clock(void) -{ - return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); -} - unsigned long long cpu_clock(int cpu) { unsigned long long clock; diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index cf2cd6c..0fe94ea 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -899,7 +899,7 @@ static void hrtick_start_fair(struct rq *rq, struct task_struct *p) * doesn't make sense. Rely on vruntime for fairness. */ if (rq->curr != p) - delta = max(10000LL, delta); + delta = max_t(s64, 10000LL, delta); hrtick_start(rq, delta); } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 825b4c0..f5da526 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -289,7 +289,6 @@ void tick_nohz_stop_sched_tick(int inidle) ts->tick_stopped = 1; ts->idle_jiffies = last_jiffies; rcu_enter_nohz(); - sched_clock_tick_stop(cpu); } /* @@ -392,7 +391,6 @@ void tick_nohz_restart_sched_tick(void) select_nohz_load_balancer(0); now = ktime_get(); tick_do_update_jiffies64(now); - sched_clock_tick_start(cpu); cpu_clear(cpu, nohz_cpu_mask); /* -- 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/