Commit 52494535 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

rcu: Reduce rcutorture tracing 



Currently, rcutorture traces every read-side access.  This can be
problematic because even a two-minute rcutorture run on a two-CPU system
can generate 28,853,363 reads.  Normally, only a failing read is of
interest, so this commit traces adjusts rcutorture's tracing to only
trace failing reads.  The resulting event tracing records the time
and the ->completed value captured at the beginning of the RCU read-side
critical section, allowing correlation with other event-tracing messages.

Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
[ paulmck: Add fix to build problem located by Randy Dunlap based on
  diagnosis by Steven Rostedt. ]
parent dc975e94

include/linux/rcupdate.h

+10 −3
Original line number Diff line number Diff line
@@ -53,7 +53,10 @@ extern int rcutorture_runnable; /* for sysctl */ 
extern void rcutorture_record_test_transition(void);

extern void rcutorture_record_progress(unsigned long vernum);

extern void do_trace_rcu_torture_read(char *rcutorturename,

				      struct rcu_head *rhp);

				      struct rcu_head *rhp,

				      unsigned long secs,

				      unsigned long c_old,

				      unsigned long c);

#else

static inline void rcutorture_record_test_transition(void)

{
@@ -63,9 +66,13 @@ static inline void rcutorture_record_progress(unsigned long vernum) 
}

#ifdef CONFIG_RCU_TRACE

extern void do_trace_rcu_torture_read(char *rcutorturename,

				      struct rcu_head *rhp);

				      struct rcu_head *rhp,

				      unsigned long secs,

				      unsigned long c_old,

				      unsigned long c);

#else

#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)

#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \

	do { } while (0)

#endif

#endif

include/trace/events/rcu.h

+14 −5
Original line number Diff line number Diff line
@@ -523,22 +523,30 @@ TRACE_EVENT(rcu_batch_end, 
 */

TRACE_EVENT(rcu_torture_read,



	TP_PROTO(char *rcutorturename, struct rcu_head *rhp),

	TP_PROTO(char *rcutorturename, struct rcu_head *rhp,

		 unsigned long secs, unsigned long c_old, unsigned long c),



	TP_ARGS(rcutorturename, rhp),

	TP_ARGS(rcutorturename, rhp, secs, c_old, c),



	TP_STRUCT__entry(

		__field(char *, rcutorturename)

		__field(struct rcu_head *, rhp)

		__field(unsigned long, secs)

		__field(unsigned long, c_old)

		__field(unsigned long, c)

	),



	TP_fast_assign(

		__entry->rcutorturename = rcutorturename;

		__entry->rhp = rhp;

		__entry->secs = secs;

		__entry->c_old = c_old;

		__entry->c = c;

	),



	TP_printk("%s torture read %p",

		  __entry->rcutorturename, __entry->rhp)

	TP_printk("%s torture read %p %luus c: %lu %lu",

		  __entry->rcutorturename, __entry->rhp,

		  __entry->secs, __entry->c_old, __entry->c)

);



/*
@@ -608,7 +616,8 @@ TRACE_EVENT(rcu_barrier, 
#define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)

#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \

	do { } while (0)

#define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)

#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \

	do { } while (0)

#define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0)



#endif /* #else #ifdef CONFIG_RCU_TRACE */

kernel/rcupdate.c

+6 −3
Original line number Diff line number Diff line
@@ -404,11 +404,14 @@ EXPORT_SYMBOL_GPL(rcuhead_debug_descr); 
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */



#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)

void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)

void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp,

			       unsigned long secs,

			       unsigned long c_old, unsigned long c)

{

	trace_rcu_torture_read(rcutorturename, rhp);

	trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);

}

EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);

#else

#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)

#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \

	do { } while (0)

#endif

kernel/rcutorture.c

+24 −7
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
#include <linux/stat.h>

#include <linux/srcu.h>

#include <linux/slab.h>

#include <linux/trace_clock.h>

#include <asm/byteorder.h>



MODULE_LICENSE("GPL");
@@ -1028,7 +1029,6 @@ void rcutorture_trace_dump(void) 
		return;

	if (atomic_xchg(&beenhere, 1) != 0)

		return;

	do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL);

	ftrace_dump(DUMP_ALL);

}
@@ -1042,13 +1042,16 @@ static void rcu_torture_timer(unsigned long unused) 
{

	int idx;

	int completed;

	int completed_end;

	static DEFINE_RCU_RANDOM(rand);

	static DEFINE_SPINLOCK(rand_lock);

	struct rcu_torture *p;

	int pipe_count;

	unsigned long long ts;



	idx = cur_ops->readlock();

	completed = cur_ops->completed();

	ts = trace_clock_local();

	p = rcu_dereference_check(rcu_torture_current,

				  rcu_read_lock_bh_held() ||

				  rcu_read_lock_sched_held() ||
@@ -1058,7 +1061,6 @@ static void rcu_torture_timer(unsigned long unused) 
		cur_ops->readunlock(idx);

		return;

	}

	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);

	if (p->rtort_mbtest == 0)

		atomic_inc(&n_rcu_torture_mberror);

	spin_lock(&rand_lock);
@@ -1071,10 +1073,16 @@ static void rcu_torture_timer(unsigned long unused) 
		/* Should not happen, but... */

		pipe_count = RCU_TORTURE_PIPE_LEN;

	}

	if (pipe_count > 1)

	completed_end = cur_ops->completed();

	if (pipe_count > 1) {

		unsigned long __maybe_unused ts_rem = do_div(ts, NSEC_PER_USEC);



		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,

					  completed, completed_end);

		rcutorture_trace_dump();

	}

	__this_cpu_inc(rcu_torture_count[pipe_count]);

	completed = cur_ops->completed() - completed;

	completed = completed_end - completed;

	if (completed > RCU_TORTURE_PIPE_LEN) {

		/* Should not happen, but... */

		completed = RCU_TORTURE_PIPE_LEN;
@@ -1094,11 +1102,13 @@ static int 
rcu_torture_reader(void *arg)

{

	int completed;

	int completed_end;

	int idx;

	DEFINE_RCU_RANDOM(rand);

	struct rcu_torture *p;

	int pipe_count;

	struct timer_list t;

	unsigned long long ts;



	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");

	set_user_nice(current, 19);
@@ -1112,6 +1122,7 @@ rcu_torture_reader(void *arg) 
		}

		idx = cur_ops->readlock();

		completed = cur_ops->completed();

		ts = trace_clock_local();

		p = rcu_dereference_check(rcu_torture_current,

					  rcu_read_lock_bh_held() ||

					  rcu_read_lock_sched_held() ||
@@ -1122,7 +1133,6 @@ rcu_torture_reader(void *arg) 
			schedule_timeout_interruptible(HZ);

			continue;

		}

		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);

		if (p->rtort_mbtest == 0)

			atomic_inc(&n_rcu_torture_mberror);

		cur_ops->read_delay(&rand);
@@ -1132,10 +1142,17 @@ rcu_torture_reader(void *arg) 
			/* Should not happen, but... */

			pipe_count = RCU_TORTURE_PIPE_LEN;

		}

		if (pipe_count > 1)

		completed_end = cur_ops->completed();

		if (pipe_count > 1) {

			unsigned long __maybe_unused ts_rem =

					do_div(ts, NSEC_PER_USEC);



			do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,

						  ts, completed, completed_end);

			rcutorture_trace_dump();

		}

		__this_cpu_inc(rcu_torture_count[pipe_count]);

		completed = cur_ops->completed() - completed;

		completed = completed_end - completed;

		if (completed > RCU_TORTURE_PIPE_LEN) {

			/* Should not happen, but... */

			completed = RCU_TORTURE_PIPE_LEN;

lib/Kconfig.debug

+1 −0
Original line number Diff line number Diff line
@@ -1008,6 +1008,7 @@ config RCU_CPU_STALL_INFO 
config RCU_TRACE

	bool "Enable tracing for RCU"

	depends on DEBUG_KERNEL

	select TRACE_CLOCK

	help

	  This option provides tracing in RCU which presents stats

	  in debugfs for debugging RCU implementation.

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