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rcu: Event-trace markers for computing RCU CPU utilization 

This commit adds the trace_rcu_utilization() marker that is to be
used to allow postprocessing scripts compute RCU's CPU utilization,
give or take event-trace overhead.  Note that we do not include RCU's
dyntick-idle interface because event tracing requires RCU protection,
which is not available in dyntick-idle mode.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2011-06-18 22:26:31 -07:00 committed by Paul E. McKenney
parent 29c00b4a1d
commit 300df91ca9
2 changed files with 69 additions and 22 deletions
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75
include/trace/events/rcu.h
View File

@ -7,29 +7,58 @@
#include <linux/tracepoint.h>
/*
* Tracepoint for calling rcu_do_batch, performed to start callback invocation:
* Tracepoint for start/end markers used for utilization calculations.
* By convention, the string is of the following forms:
*
* "Start <activity>" -- Mark the start of the specified activity,
* such as "context switch". Nesting is permitted.
* "End <activity>" -- Mark the end of the specified activity.
*/
TRACE_EVENT(rcu_batch_start,
TRACE_EVENT(rcu_utilization,
TP_PROTO(long callbacks_ready, int blimit),
TP_PROTO(char *s),
TP_ARGS(callbacks_ready, blimit),
TP_ARGS(s),
TP_STRUCT__entry(
__field( long, callbacks_ready )
__field( int, blimit )
__field(char *, s)
),
TP_fast_assign(
__entry->callbacks_ready = callbacks_ready;
__entry->blimit = blimit;
__entry->s = s;
),
TP_printk("CBs=%ld bl=%d", __entry->callbacks_ready, __entry->blimit)
TP_printk("%s", __entry->s)
);
/*
* Tracepoint for the invocation of a single RCU callback
* Tracepoint for marking the beginning rcu_do_batch, performed to start
* RCU callback invocation. The first argument is the total number of
* callbacks (including those that are not yet ready to be invoked),
* and the second argument is the current RCU-callback batch limit.
*/
TRACE_EVENT(rcu_batch_start,
TP_PROTO(long qlen, int blimit),
TP_ARGS(qlen, blimit),
TP_STRUCT__entry(
__field(long, qlen)
__field(int, blimit)
),
TP_fast_assign(
__entry->qlen = qlen;
__entry->blimit = blimit;
),
TP_printk("CBs=%ld bl=%d", __entry->qlen, __entry->blimit)
);
/*
* Tracepoint for the invocation of a single RCU callback function.
* The argument is a pointer to the RCU callback itself.
*/
TRACE_EVENT(rcu_invoke_callback,
@ -38,20 +67,23 @@ TRACE_EVENT(rcu_invoke_callback,
TP_ARGS(rhp),
TP_STRUCT__entry(
__field( void *, rhp )
__field( void *, func )
__field(void *, rhp)
__field(void *, func)
),
TP_fast_assign(
__entry->rhp = rhp;
__entry->func = rhp->func;
__entry->rhp = rhp;
__entry->func = rhp->func;
),
TP_printk("rhp=%p func=%pf", __entry->rhp, __entry->func)
);
/*
* Tracepoint for the invocation of a single RCU kfree callback
* Tracepoint for the invocation of a single RCU callback of the special
* kfree() form. The first argument is a pointer to the RCU callback
* and the second argument is the offset of the callback within the
* enclosing RCU-protected data structure.
*/
TRACE_EVENT(rcu_invoke_kfree_callback,
@ -60,12 +92,12 @@ TRACE_EVENT(rcu_invoke_kfree_callback,
TP_ARGS(rhp, offset),
TP_STRUCT__entry(
__field(void *, rhp )
__field(unsigned long, offset )
__field(void *, rhp)
__field(unsigned long, offset)
),
TP_fast_assign(
__entry->rhp = rhp;
__entry->rhp = rhp;
__entry->offset = offset;
),
@ -73,7 +105,8 @@ TRACE_EVENT(rcu_invoke_kfree_callback,
);
/*
* Tracepoint for leaving rcu_do_batch, performed after callback invocation:
* Tracepoint for exiting rcu_do_batch after RCU callbacks have been
* invoked. The first argument is the number of callbacks actually invoked.
*/
TRACE_EVENT(rcu_batch_end,
@ -82,11 +115,11 @@ TRACE_EVENT(rcu_batch_end,
TP_ARGS(callbacks_invoked),
TP_STRUCT__entry(
__field( int, callbacks_invoked )
__field(int, callbacks_invoked)
),
TP_fast_assign(
__entry->callbacks_invoked = callbacks_invoked;
__entry->callbacks_invoked = callbacks_invoked;
),
TP_printk("CBs-invoked=%d", __entry->callbacks_invoked)

16
kernel/rcutree.c
View File

@ -184,8 +184,10 @@ void rcu_bh_qs(int cpu)
*/
void rcu_note_context_switch(int cpu)
{
trace_rcu_utilization("Start context switch");
rcu_sched_qs(cpu);
rcu_preempt_note_context_switch(cpu);
trace_rcu_utilization("End context switch");
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
@ -1275,6 +1277,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
*/
void rcu_check_callbacks(int cpu, int user)
{
trace_rcu_utilization("Start scheduler-tick");
if (user ||
(idle_cpu(cpu) && rcu_scheduler_active &&
!in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
@ -1308,6 +1311,7 @@ void rcu_check_callbacks(int cpu, int user)
rcu_preempt_check_callbacks(cpu);
if (rcu_pending(cpu))
invoke_rcu_core();
trace_rcu_utilization("End scheduler-tick");
}
#ifdef CONFIG_SMP
@ -1369,10 +1373,14 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
unsigned long flags;
struct rcu_node *rnp = rcu_get_root(rsp);
if (!rcu_gp_in_progress(rsp))
trace_rcu_utilization("Start fqs");
if (!rcu_gp_in_progress(rsp)) {
trace_rcu_utilization("End fqs");
return; /* No grace period in progress, nothing to force. */
}
if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
trace_rcu_utilization("End fqs");
return; /* Someone else is already on the job. */
}
if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
@ -1421,11 +1429,13 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
rsp->fqs_need_gp = 0;
rcu_start_gp(rsp, flags); /* releases rnp->lock */
trace_rcu_utilization("End fqs");
return;
}
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
unlock_fqs_ret:
raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
trace_rcu_utilization("End fqs");
}
#else /* #ifdef CONFIG_SMP */
@ -1481,6 +1491,7 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
*/
static void rcu_process_callbacks(struct softirq_action *unused)
{
trace_rcu_utilization("Start RCU core");
__rcu_process_callbacks(&rcu_sched_state,
&__get_cpu_var(rcu_sched_data));
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
@ -1488,6 +1499,7 @@ static void rcu_process_callbacks(struct softirq_action *unused)
/* If we are last CPU on way to dyntick-idle mode, accelerate it. */
rcu_needs_cpu_flush();
trace_rcu_utilization("End RCU core");
}
/*
@ -1910,6 +1922,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
trace_rcu_utilization("Start CPU hotplug");
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
@ -1945,6 +1958,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
default:
break;
}
trace_rcu_utilization("End CPU hotplug");
return NOTIFY_OK;
}