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authorFrederic Weisbecker <fweisbec@gmail.com>2012-07-16 18:00:34 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2013-01-27 19:23:29 +0100
commit3f4724ea85b7d9055a9976fa8f30b471bdfbca93 (patch)
treeaaa1792d0b78ea33c07ee6f5e707a07d9ef1795e /kernel/sched
parentabf917cd91cbb73952758f9741e2fa65002a48ee (diff)
downloadlinaro-lsk-3f4724ea85b7d9055a9976fa8f30b471bdfbca93.tar.gz
cputime: Allow dynamic switch between tick/virtual based cputime accounting
Allow to dynamically switch between tick and virtual based cputime accounting. This way we can provide a kind of "on-demand" virtual based cputime accounting. In this mode, the kernel relies on the context tracking subsystem to dynamically probe on kernel boundaries. This is in preparation for being able to stop the timer tick in more places than just the idle state. Doing so will depend on CONFIG_VIRT_CPU_ACCOUNTING_GEN which makes it possible to account the cputime without the tick by hooking on kernel/user boundaries. Depending whether the tick is stopped or not, we can switch between tick and vtime based accounting anytime in order to minimize the overhead associated to user hooks. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/cputime.c41
1 files changed, 31 insertions, 10 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 1c964eced92..e1939d38bf7 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -317,8 +317,6 @@ out:
rcu_read_unlock();
}
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
/*
* Account a tick to a process and cpustat
@@ -383,11 +381,12 @@ static void irqtime_account_idle_ticks(int ticks)
irqtime_account_process_tick(current, 0, rq);
}
#else /* CONFIG_IRQ_TIME_ACCOUNTING */
-static void irqtime_account_idle_ticks(int ticks) {}
-static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
+static inline void irqtime_account_idle_ticks(int ticks) {}
+static inline void irqtime_account_process_tick(struct task_struct *p, int user_tick,
struct rq *rq) {}
#endif /* CONFIG_IRQ_TIME_ACCOUNTING */
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
/*
* Account a single tick of cpu time.
* @p: the process that the cpu time gets accounted to
@@ -398,6 +397,9 @@ void account_process_tick(struct task_struct *p, int user_tick)
cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
struct rq *rq = this_rq();
+ if (vtime_accounting_enabled())
+ return;
+
if (sched_clock_irqtime) {
irqtime_account_process_tick(p, user_tick, rq);
return;
@@ -439,8 +441,7 @@ void account_idle_ticks(unsigned long ticks)
account_idle_time(jiffies_to_cputime(ticks));
}
-
-#endif
+#endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
/*
* Use precise platform statistics if available:
@@ -475,6 +476,9 @@ EXPORT_SYMBOL_GPL(vtime_account_system_irqsafe);
#ifndef __ARCH_HAS_VTIME_TASK_SWITCH
void vtime_task_switch(struct task_struct *prev)
{
+ if (!vtime_accounting_enabled())
+ return;
+
if (is_idle_task(prev))
vtime_account_idle(prev);
else
@@ -498,6 +502,9 @@ void vtime_task_switch(struct task_struct *prev)
#ifndef __ARCH_HAS_VTIME_ACCOUNT
void vtime_account(struct task_struct *tsk)
{
+ if (!vtime_accounting_enabled())
+ return;
+
if (!in_interrupt()) {
/*
* If we interrupted user, context_tracking_in_user()
@@ -520,7 +527,7 @@ void vtime_account(struct task_struct *tsk)
EXPORT_SYMBOL_GPL(vtime_account);
#endif /* __ARCH_HAS_VTIME_ACCOUNT */
-#else
+#else /* !CONFIG_VIRT_CPU_ACCOUNTING */
static cputime_t scale_utime(cputime_t utime, cputime_t rtime, cputime_t total)
{
@@ -599,7 +606,7 @@ void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime
thread_group_cputime(p, &cputime);
cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);
}
-#endif
+#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static DEFINE_PER_CPU(unsigned long long, cputime_snap);
@@ -617,14 +624,23 @@ static cputime_t get_vtime_delta(void)
void vtime_account_system(struct task_struct *tsk)
{
- cputime_t delta_cpu = get_vtime_delta();
+ cputime_t delta_cpu;
+
+ if (!vtime_accounting_enabled())
+ return;
+ delta_cpu = get_vtime_delta();
account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
}
void vtime_account_user(struct task_struct *tsk)
{
- cputime_t delta_cpu = get_vtime_delta();
+ cputime_t delta_cpu;
+
+ if (!vtime_accounting_enabled())
+ return;
+
+ delta_cpu = get_vtime_delta();
account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
}
@@ -635,4 +651,9 @@ void vtime_account_idle(struct task_struct *tsk)
account_idle_time(delta_cpu);
}
+
+bool vtime_accounting_enabled(void)
+{
+ return context_tracking_active();
+}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */