Commit 71107445 authored by Jason Low's avatar Jason Low Committed by Ingo Molnar
Browse files

sched, timer: Use the atomic task_cputime in thread_group_cputimer 



Recent optimizations were made to thread_group_cputimer to improve its
scalability by keeping track of cputime stats without a lock. However,
the values were open coded to the structure, causing them to be at
a different abstraction level from the regular task_cputime structure.
Furthermore, any subsequent similar optimizations would not be able to
share the new code, since they are specific to thread_group_cputimer.

This patch adds the new task_cputime_atomic data structure (introduced in
the previous patch in the series) to thread_group_cputimer for keeping
track of the cputime atomically, which also helps generalize the code.

Suggested-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarJason Low <jason.low2@hp.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1430251224-5764-6-git-send-email-jason.low2@hp.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 971e8a98

include/linux/init_task.h

+2 −4
Original line number Diff line number Diff line
@@ -50,10 +50,8 @@ extern struct fs_struct init_fs; 
	.cpu_timers	= INIT_CPU_TIMERS(sig.cpu_timers),		\

	.rlim		= INIT_RLIMITS,					\

	.cputimer	= { 						\

		.utime 		  = ATOMIC64_INIT(0),			\

		.stime		  = ATOMIC64_INIT(0),			\

		.sum_exec_runtime = ATOMIC64_INIT(0),			\

		.running 	  = 0					\

		.cputime_atomic	= INIT_CPUTIME_ATOMIC,			\

		.running	= 0,					\

	},								\

	.cred_guard_mutex =						\

		 __MUTEX_INITIALIZER(sig.cred_guard_mutex),		\

include/linux/sched.h

+1 −3
Original line number Diff line number Diff line
@@ -615,9 +615,7 @@ struct task_cputime_atomic { 
 * used for thread group CPU timer calculations.

 */

struct thread_group_cputimer {

	atomic64_t utime;

	atomic64_t stime;

	atomic64_t sum_exec_runtime;

	struct task_cputime_atomic cputime_atomic;

	int running;

};

kernel/sched/stats.h

+3 −3
Original line number Diff line number Diff line
@@ -216,7 +216,7 @@ static inline void account_group_user_time(struct task_struct *tsk, 
	if (!cputimer_running(tsk))

		return;



	atomic64_add(cputime, &cputimer->utime);

	atomic64_add(cputime, &cputimer->cputime_atomic.utime);

}



/**
@@ -237,7 +237,7 @@ static inline void account_group_system_time(struct task_struct *tsk, 
	if (!cputimer_running(tsk))

		return;



	atomic64_add(cputime, &cputimer->stime);

	atomic64_add(cputime, &cputimer->cputime_atomic.stime);

}



/**
@@ -258,5 +258,5 @@ static inline void account_group_exec_runtime(struct task_struct *tsk, 
	if (!cputimer_running(tsk))

		return;



	atomic64_add(ns, &cputimer->sum_exec_runtime);

	atomic64_add(ns, &cputimer->cputime_atomic.sum_exec_runtime);

}

kernel/time/posix-cpu-timers.c

+13 −13
Original line number Diff line number Diff line
@@ -211,20 +211,20 @@ retry: 
	}

}



static void update_gt_cputime(struct thread_group_cputimer *cputimer, struct task_cputime *sum)

static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)

{

	__update_gt_cputime(&cputimer->utime, sum->utime);

	__update_gt_cputime(&cputimer->stime, sum->stime);

	__update_gt_cputime(&cputimer->sum_exec_runtime, sum->sum_exec_runtime);

	__update_gt_cputime(&cputime_atomic->utime, sum->utime);

	__update_gt_cputime(&cputime_atomic->stime, sum->stime);

	__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);

}



/* Sample thread_group_cputimer values in "cputimer", store results in "times". */

static inline void sample_group_cputimer(struct task_cputime *times,

					  struct thread_group_cputimer *cputimer)

/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */

static inline void sample_cputime_atomic(struct task_cputime *times,

					 struct task_cputime_atomic *atomic_times)

{

	times->utime = atomic64_read(&cputimer->utime);

	times->stime = atomic64_read(&cputimer->stime);

	times->sum_exec_runtime = atomic64_read(&cputimer->sum_exec_runtime);

	times->utime = atomic64_read(&atomic_times->utime);

	times->stime = atomic64_read(&atomic_times->stime);

	times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);

}



void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
@@ -240,7 +240,7 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times) 
		 * to synchronize the timer to the clock every time we start it.

		 */

		thread_group_cputime(tsk, &sum);

		update_gt_cputime(cputimer, &sum);

		update_gt_cputime(&cputimer->cputime_atomic, &sum);



		/*

		 * We're setting cputimer->running without a lock. Ensure
@@ -251,7 +251,7 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times) 
		 */

		WRITE_ONCE(cputimer->running, 1);

	}

	sample_group_cputimer(times, cputimer);

	sample_cputime_atomic(times, &cputimer->cputime_atomic);

}



/*
@@ -1137,7 +1137,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk) 
	if (READ_ONCE(sig->cputimer.running)) {

		struct task_cputime group_sample;



		sample_group_cputimer(&group_sample, &sig->cputimer);

		sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);



		if (task_cputime_expired(&group_sample, &sig->cputime_expires))

			return 1;

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