From 300df91ca9358f7f09298eec9503c12b32054ef7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 18 Jun 2011 22:26:31 -0700 Subject: [PATCH] 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 Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 73 +++++++++++++++++++++++++++----------- kernel/rcutree.c | 16 ++++++++- 2 files changed, 68 insertions(+), 21 deletions(-) diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index db3f6e9e63e..ab458eb689f 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -7,29 +7,58 @@ #include /* - * 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 " -- Mark the start of the specified activity, + * such as "context switch". Nesting is permitted. + * "End " -- Mark the end of the specified activity. + */ +TRACE_EVENT(rcu_utilization, + + TP_PROTO(char *s), + + TP_ARGS(s), + + TP_STRUCT__entry( + __field(char *, s) + ), + + TP_fast_assign( + __entry->s = s; + ), + + TP_printk("%s", __entry->s) +); + +/* + * 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 callbacks_ready, int blimit), + TP_PROTO(long qlen, int blimit), - TP_ARGS(callbacks_ready, blimit), + TP_ARGS(qlen, blimit), TP_STRUCT__entry( - __field( long, callbacks_ready ) - __field( int, blimit ) + __field(long, qlen) + __field(int, blimit) ), TP_fast_assign( - __entry->callbacks_ready = callbacks_ready; - __entry->blimit = blimit; + __entry->qlen = qlen; + __entry->blimit = blimit; ), - TP_printk("CBs=%ld bl=%d", __entry->callbacks_ready, __entry->blimit) + TP_printk("CBs=%ld bl=%d", __entry->qlen, __entry->blimit) ); /* - * Tracepoint for the invocation of a single RCU callback + * 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) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 45dcc2036a1..2a9643bd6ae 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -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; } -- 2.39.2