Commit fa13a5a1 authored by Paul Mackerras's avatar Paul Mackerras Committed by Ingo Molnar
Browse files

sched: restore deterministic CPU accounting on powerpc 



Since powerpc started using CONFIG_GENERIC_CLOCKEVENTS, the
deterministic CPU accounting (CONFIG_VIRT_CPU_ACCOUNTING) has been
broken on powerpc, because we end up counting user time twice: once in
timer_interrupt() and once in update_process_times().

This fixes the problem by pulling the code in update_process_times
that updates utime and stime into a separate function called
account_process_tick.  If CONFIG_VIRT_CPU_ACCOUNTING is not defined,
there is a version of account_process_tick in kernel/timer.c that
simply accounts a whole tick to either utime or stime as before.  If
CONFIG_VIRT_CPU_ACCOUNTING is defined, then arch code gets to
implement account_process_tick.

This also lets us simplify the s390 code a bit; it means that the s390
timer interrupt can now call update_process_times even when
CONFIG_VIRT_CPU_ACCOUNTING is turned on, and can just implement a
suitable account_process_tick().

account_process_tick() now takes the task_struct * as an argument.
Tested both with and without CONFIG_VIRT_CPU_ACCOUNTING.

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9a41785c

arch/powerpc/kernel/process.c

+1 −1
Original line number Diff line number Diff line
@@ -350,7 +350,7 @@ struct task_struct *__switch_to(struct task_struct *prev, 
	local_irq_save(flags);



	account_system_vtime(current);

	account_process_vtime(current);

	account_process_tick(current, 0);

	calculate_steal_time();



	last = _switch(old_thread, new_thread);

arch/powerpc/kernel/time.c

+1 −24
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ void account_system_vtime(struct task_struct *tsk) 
 * user and system time records.

 * Must be called with interrupts disabled.

 */

void account_process_vtime(struct task_struct *tsk)

void account_process_tick(struct task_struct *tsk, int user_tick)

{

	cputime_t utime, utimescaled;
@@ -274,18 +274,6 @@ void account_process_vtime(struct task_struct *tsk) 
	account_user_time_scaled(tsk, utimescaled);

}



static void account_process_time(struct pt_regs *regs)

{

	int cpu = smp_processor_id();



	account_process_vtime(current);

	run_local_timers();

	if (rcu_pending(cpu))

		rcu_check_callbacks(cpu, user_mode(regs));

	scheduler_tick();

 	run_posix_cpu_timers(current);

}



/*

 * Stuff for accounting stolen time.

 */
@@ -375,7 +363,6 @@ static void snapshot_purr(void) 


#else /* ! CONFIG_VIRT_CPU_ACCOUNTING */

#define calc_cputime_factors()

#define account_process_time(regs)	update_process_times(user_mode(regs))

#define calculate_steal_time()		do { } while (0)

#endif
@@ -599,16 +586,6 @@ void timer_interrupt(struct pt_regs * regs) 
		get_lppaca()->int_dword.fields.decr_int = 0;

#endif



	/*

	 * We cannot disable the decrementer, so in the period

	 * between this cpu's being marked offline in cpu_online_map

	 * and calling stop-self, it is taking timer interrupts.

	 * Avoid calling into the scheduler rebalancing code if this

	 * is the case.

	 */

	if (!cpu_is_offline(cpu))

		account_process_time(regs);



	if (evt->event_handler)

		evt->event_handler(evt);

	else

arch/s390/kernel/time.c

+0 −4
Original line number Diff line number Diff line
@@ -145,12 +145,8 @@ void account_ticks(u64 time) 
	do_timer(ticks);

#endif



#ifdef CONFIG_VIRT_CPU_ACCOUNTING

	account_tick_vtime(current);

#else

	while (ticks--)

		update_process_times(user_mode(get_irq_regs()));

#endif



	s390_do_profile();

}

arch/s390/kernel/vtime.c

+1 −7
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer); 
 * Update process times based on virtual cpu times stored by entry.S

 * to the lowcore fields user_timer, system_timer & steal_clock.

 */

void account_tick_vtime(struct task_struct *tsk)

void account_process_tick(struct task_struct *tsk, int user_tick)

{

	cputime_t cputime;

	__u64 timer, clock;
@@ -64,12 +64,6 @@ void account_tick_vtime(struct task_struct *tsk) 
		S390_lowcore.steal_clock -= cputime << 12;

		account_steal_time(tsk, cputime);

	}



	run_local_timers();

	if (rcu_pending(smp_processor_id()))

		rcu_check_callbacks(smp_processor_id(), rcu_user_flag);

	scheduler_tick();

 	run_posix_cpu_timers(tsk);

}



/*

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -254,6 +254,7 @@ long io_schedule_timeout(long timeout); 


extern void cpu_init (void);

extern void trap_init(void);

extern void account_process_tick(struct task_struct *task, int user);

extern void update_process_times(int user);

extern void scheduler_tick(void);

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