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![Martin Schwidefsky](/assets/img/avatar_default.png)
The cpu time spent by the idle process actually doing something is currently accounted as idle time. This is plain wrong, the architectures that support VIRT_CPU_ACCOUNTING=y can do better: distinguish between the time spent doing nothing and the time spent by idle doing work. The first is accounted with account_idle_time and the second with account_system_time. The architectures that use the account_xxx_time interface directly and not the account_xxx_ticks interface now need to do the check for the idle process in their arch code. In particular to improve the system vs true idle time accounting the arch code needs to measure the true idle time instead of just testing for the idle process. To improve the tick based accounting as well we would need an architecture primitive that can tell us if the pt_regs of the interrupted context points to the magic instruction that halts the cpu. In addition idle time is no more added to the stime of the idle process. This field now contains the system time of the idle process as it should be. On systems without VIRT_CPU_ACCOUNTING this will always be zero as every tick that occurs while idle is running will be accounted as idle time. This patch contains the necessary common code changes to be able to distinguish idle system time and true idle time. The architectures with support for VIRT_CPU_ACCOUNTING need some changes to exploit this. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
480 lines
13 KiB
C
480 lines
13 KiB
C
/*
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* linux/arch/ia64/kernel/time.c
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*
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* Copyright (C) 1998-2003 Hewlett-Packard Co
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* Stephane Eranian <eranian@hpl.hp.com>
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* David Mosberger <davidm@hpl.hp.com>
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* Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
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* Copyright (C) 1999-2000 VA Linux Systems
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* Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
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*/
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#include <linux/cpu.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/profile.h>
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#include <linux/sched.h>
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#include <linux/time.h>
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#include <linux/interrupt.h>
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#include <linux/efi.h>
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#include <linux/timex.h>
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#include <linux/clocksource.h>
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#include <asm/machvec.h>
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#include <asm/delay.h>
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#include <asm/hw_irq.h>
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#include <asm/paravirt.h>
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#include <asm/ptrace.h>
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#include <asm/sal.h>
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#include <asm/sections.h>
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#include <asm/system.h>
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#include "fsyscall_gtod_data.h"
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static cycle_t itc_get_cycles(void);
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struct fsyscall_gtod_data_t fsyscall_gtod_data = {
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.lock = SEQLOCK_UNLOCKED,
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};
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struct itc_jitter_data_t itc_jitter_data;
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volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
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#ifdef CONFIG_IA64_DEBUG_IRQ
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unsigned long last_cli_ip;
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EXPORT_SYMBOL(last_cli_ip);
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#endif
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#ifdef CONFIG_PARAVIRT
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static void
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paravirt_clocksource_resume(void)
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{
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if (pv_time_ops.clocksource_resume)
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pv_time_ops.clocksource_resume();
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}
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#endif
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static struct clocksource clocksource_itc = {
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.name = "itc",
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.rating = 350,
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.read = itc_get_cycles,
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.mask = CLOCKSOURCE_MASK(64),
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.mult = 0, /*to be calculated*/
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.shift = 16,
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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#ifdef CONFIG_PARAVIRT
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.resume = paravirt_clocksource_resume,
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#endif
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};
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static struct clocksource *itc_clocksource;
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING
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#include <linux/kernel_stat.h>
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extern cputime_t cycle_to_cputime(u64 cyc);
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/*
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* Called from the context switch with interrupts disabled, to charge all
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* accumulated times to the current process, and to prepare accounting on
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* the next process.
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*/
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void ia64_account_on_switch(struct task_struct *prev, struct task_struct *next)
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{
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struct thread_info *pi = task_thread_info(prev);
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struct thread_info *ni = task_thread_info(next);
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cputime_t delta_stime, delta_utime;
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__u64 now;
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now = ia64_get_itc();
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delta_stime = cycle_to_cputime(pi->ac_stime + (now - pi->ac_stamp));
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if (idle_task(smp_processor_id()) != prev)
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account_system_time(prev, 0, delta_stime, delta_stime);
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else
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account_idle_time(delta_stime);
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if (pi->ac_utime) {
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delta_utime = cycle_to_cputime(pi->ac_utime);
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account_user_time(prev, delta_utime, delta_utime);
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}
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pi->ac_stamp = ni->ac_stamp = now;
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ni->ac_stime = ni->ac_utime = 0;
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}
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/*
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* Account time for a transition between system, hard irq or soft irq state.
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* Note that this function is called with interrupts enabled.
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*/
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void account_system_vtime(struct task_struct *tsk)
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{
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struct thread_info *ti = task_thread_info(tsk);
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unsigned long flags;
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cputime_t delta_stime;
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__u64 now;
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local_irq_save(flags);
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now = ia64_get_itc();
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delta_stime = cycle_to_cputime(ti->ac_stime + (now - ti->ac_stamp));
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if (irq_count() || idle_task(smp_processor_id()) != tsk)
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account_system_time(tsk, 0, delta_stime, delta_stime);
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else
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account_idle_time(delta_stime);
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ti->ac_stime = 0;
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ti->ac_stamp = now;
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(account_system_vtime);
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/*
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* Called from the timer interrupt handler to charge accumulated user time
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* to the current process. Must be called with interrupts disabled.
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*/
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void account_process_tick(struct task_struct *p, int user_tick)
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{
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struct thread_info *ti = task_thread_info(p);
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cputime_t delta_utime;
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if (ti->ac_utime) {
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delta_utime = cycle_to_cputime(ti->ac_utime);
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account_user_time(p, delta_utime, delta_utime);
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ti->ac_utime = 0;
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}
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}
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#endif /* CONFIG_VIRT_CPU_ACCOUNTING */
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static irqreturn_t
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timer_interrupt (int irq, void *dev_id)
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{
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unsigned long new_itm;
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if (unlikely(cpu_is_offline(smp_processor_id()))) {
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return IRQ_HANDLED;
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}
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platform_timer_interrupt(irq, dev_id);
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new_itm = local_cpu_data->itm_next;
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if (!time_after(ia64_get_itc(), new_itm))
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printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
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ia64_get_itc(), new_itm);
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profile_tick(CPU_PROFILING);
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if (paravirt_do_steal_accounting(&new_itm))
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goto skip_process_time_accounting;
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while (1) {
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update_process_times(user_mode(get_irq_regs()));
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new_itm += local_cpu_data->itm_delta;
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if (smp_processor_id() == time_keeper_id) {
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/*
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* Here we are in the timer irq handler. We have irqs locally
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* disabled, but we don't know if the timer_bh is running on
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* another CPU. We need to avoid to SMP race by acquiring the
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* xtime_lock.
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*/
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write_seqlock(&xtime_lock);
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do_timer(1);
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local_cpu_data->itm_next = new_itm;
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write_sequnlock(&xtime_lock);
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} else
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local_cpu_data->itm_next = new_itm;
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if (time_after(new_itm, ia64_get_itc()))
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break;
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/*
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* Allow IPIs to interrupt the timer loop.
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*/
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local_irq_enable();
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local_irq_disable();
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}
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skip_process_time_accounting:
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do {
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/*
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* If we're too close to the next clock tick for
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* comfort, we increase the safety margin by
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* intentionally dropping the next tick(s). We do NOT
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* update itm.next because that would force us to call
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* do_timer() which in turn would let our clock run
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* too fast (with the potentially devastating effect
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* of losing monotony of time).
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*/
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while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
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new_itm += local_cpu_data->itm_delta;
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ia64_set_itm(new_itm);
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/* double check, in case we got hit by a (slow) PMI: */
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} while (time_after_eq(ia64_get_itc(), new_itm));
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return IRQ_HANDLED;
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}
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/*
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* Encapsulate access to the itm structure for SMP.
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*/
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void
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ia64_cpu_local_tick (void)
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{
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int cpu = smp_processor_id();
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unsigned long shift = 0, delta;
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/* arrange for the cycle counter to generate a timer interrupt: */
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ia64_set_itv(IA64_TIMER_VECTOR);
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delta = local_cpu_data->itm_delta;
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/*
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* Stagger the timer tick for each CPU so they don't occur all at (almost) the
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* same time:
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*/
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if (cpu) {
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unsigned long hi = 1UL << ia64_fls(cpu);
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shift = (2*(cpu - hi) + 1) * delta/hi/2;
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}
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local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
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ia64_set_itm(local_cpu_data->itm_next);
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}
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static int nojitter;
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static int __init nojitter_setup(char *str)
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{
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nojitter = 1;
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printk("Jitter checking for ITC timers disabled\n");
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return 1;
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}
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__setup("nojitter", nojitter_setup);
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void __devinit
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ia64_init_itm (void)
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{
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unsigned long platform_base_freq, itc_freq;
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struct pal_freq_ratio itc_ratio, proc_ratio;
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long status, platform_base_drift, itc_drift;
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/*
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* According to SAL v2.6, we need to use a SAL call to determine the platform base
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* frequency and then a PAL call to determine the frequency ratio between the ITC
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* and the base frequency.
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*/
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status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
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&platform_base_freq, &platform_base_drift);
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if (status != 0) {
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printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
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} else {
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status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
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if (status != 0)
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printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
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}
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if (status != 0) {
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/* invent "random" values */
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printk(KERN_ERR
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"SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
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platform_base_freq = 100000000;
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platform_base_drift = -1; /* no drift info */
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itc_ratio.num = 3;
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itc_ratio.den = 1;
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}
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if (platform_base_freq < 40000000) {
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printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
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platform_base_freq);
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platform_base_freq = 75000000;
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platform_base_drift = -1;
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}
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if (!proc_ratio.den)
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proc_ratio.den = 1; /* avoid division by zero */
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if (!itc_ratio.den)
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itc_ratio.den = 1; /* avoid division by zero */
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itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
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local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
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printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
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"ITC freq=%lu.%03luMHz", smp_processor_id(),
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platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
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itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
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if (platform_base_drift != -1) {
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itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
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printk("+/-%ldppm\n", itc_drift);
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} else {
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itc_drift = -1;
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printk("\n");
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}
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local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
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local_cpu_data->itc_freq = itc_freq;
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local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
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local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
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+ itc_freq/2)/itc_freq;
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if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
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#ifdef CONFIG_SMP
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/* On IA64 in an SMP configuration ITCs are never accurately synchronized.
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* Jitter compensation requires a cmpxchg which may limit
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* the scalability of the syscalls for retrieving time.
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* The ITC synchronization is usually successful to within a few
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* ITC ticks but this is not a sure thing. If you need to improve
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* timer performance in SMP situations then boot the kernel with the
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* "nojitter" option. However, doing so may result in time fluctuating (maybe
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* even going backward) if the ITC offsets between the individual CPUs
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* are too large.
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*/
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if (!nojitter)
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itc_jitter_data.itc_jitter = 1;
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#endif
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} else
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/*
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* ITC is drifty and we have not synchronized the ITCs in smpboot.c.
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* ITC values may fluctuate significantly between processors.
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* Clock should not be used for hrtimers. Mark itc as only
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* useful for boot and testing.
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*
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* Note that jitter compensation is off! There is no point of
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* synchronizing ITCs since they may be large differentials
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* that change over time.
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*
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* The only way to fix this would be to repeatedly sync the
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* ITCs. Until that time we have to avoid ITC.
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*/
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clocksource_itc.rating = 50;
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paravirt_init_missing_ticks_accounting(smp_processor_id());
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/* avoid softlock up message when cpu is unplug and plugged again. */
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touch_softlockup_watchdog();
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/* Setup the CPU local timer tick */
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ia64_cpu_local_tick();
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if (!itc_clocksource) {
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/* Sort out mult/shift values: */
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clocksource_itc.mult =
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clocksource_hz2mult(local_cpu_data->itc_freq,
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clocksource_itc.shift);
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clocksource_register(&clocksource_itc);
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itc_clocksource = &clocksource_itc;
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}
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}
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static cycle_t itc_get_cycles(void)
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{
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u64 lcycle, now, ret;
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if (!itc_jitter_data.itc_jitter)
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return get_cycles();
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lcycle = itc_jitter_data.itc_lastcycle;
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now = get_cycles();
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if (lcycle && time_after(lcycle, now))
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return lcycle;
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/*
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* Keep track of the last timer value returned.
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* In an SMP environment, you could lose out in contention of
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* cmpxchg. If so, your cmpxchg returns new value which the
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* winner of contention updated to. Use the new value instead.
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*/
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ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, now);
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if (unlikely(ret != lcycle))
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return ret;
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return now;
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}
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static struct irqaction timer_irqaction = {
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.handler = timer_interrupt,
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.flags = IRQF_DISABLED | IRQF_IRQPOLL,
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.name = "timer"
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};
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void __init
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time_init (void)
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{
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register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
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efi_gettimeofday(&xtime);
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ia64_init_itm();
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/*
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* Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
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* tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
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*/
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set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
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}
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/*
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* Generic udelay assumes that if preemption is allowed and the thread
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* migrates to another CPU, that the ITC values are synchronized across
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* all CPUs.
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*/
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static void
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ia64_itc_udelay (unsigned long usecs)
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{
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unsigned long start = ia64_get_itc();
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unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
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while (time_before(ia64_get_itc(), end))
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cpu_relax();
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}
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void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
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void
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udelay (unsigned long usecs)
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{
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(*ia64_udelay)(usecs);
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}
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EXPORT_SYMBOL(udelay);
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/* IA64 doesn't cache the timezone */
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void update_vsyscall_tz(void)
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{
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}
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void update_vsyscall(struct timespec *wall, struct clocksource *c)
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{
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unsigned long flags;
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write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
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/* copy fsyscall clock data */
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fsyscall_gtod_data.clk_mask = c->mask;
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fsyscall_gtod_data.clk_mult = c->mult;
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fsyscall_gtod_data.clk_shift = c->shift;
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fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
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fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
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/* copy kernel time structures */
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fsyscall_gtod_data.wall_time.tv_sec = wall->tv_sec;
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fsyscall_gtod_data.wall_time.tv_nsec = wall->tv_nsec;
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fsyscall_gtod_data.monotonic_time.tv_sec = wall_to_monotonic.tv_sec
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+ wall->tv_sec;
|
|
fsyscall_gtod_data.monotonic_time.tv_nsec = wall_to_monotonic.tv_nsec
|
|
+ wall->tv_nsec;
|
|
|
|
/* normalize */
|
|
while (fsyscall_gtod_data.monotonic_time.tv_nsec >= NSEC_PER_SEC) {
|
|
fsyscall_gtod_data.monotonic_time.tv_nsec -= NSEC_PER_SEC;
|
|
fsyscall_gtod_data.monotonic_time.tv_sec++;
|
|
}
|
|
|
|
write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
|
|
}
|
|
|