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: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
[ paulmck: Add fix to build problem located by Randy Dunlap based on
diagnosis by Steven Rostedt. ]
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index a2cf761..303359d 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -404,11 +404,14 @@
#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
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 31dea01..a583f1c 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -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 @@
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 @@
{
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 @@
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 @@
/* 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 @@
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 @@
}
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 @@
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 @@
/* 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;