tracing, sched: LTTng instrumentation - scheduler
Instrument the scheduler activity (sched_switch, migration, wakeups,
wait for a task, signal delivery) and process/thread
creation/destruction (fork, exit, kthread stop). Actually, kthread
creation is not instrumented in this patch because it is architecture
dependent. It allows to connect tracers such as ftrace which detects
scheduling latencies, good/bad scheduler decisions. Tools like LTTng can
export this scheduler information along with instrumentation of the rest
of the kernel activity to perform post-mortem analysis on the scheduler
activity.
About the performance impact of tracepoints (which is comparable to
markers), even without immediate values optimizations, tests done by
Hideo Aoki on ia64 show no regression. His test case was using hackbench
on a kernel where scheduler instrumentation (about 5 events in code
scheduler code) was added. See the "Tracepoints" patch header for
performance result detail.
Changelog :
- Change instrumentation location and parameter to match ftrace
instrumentation, previously done with kernel markers.
[ mingo@elte.hu: conflict resolutions ]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: 'Peter Zijlstra' <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/trace/sched.h b/include/trace/sched.h
new file mode 100644
index 0000000..506ae13
--- /dev/null
+++ b/include/trace/sched.h
@@ -0,0 +1,45 @@
+#ifndef _TRACE_SCHED_H
+#define _TRACE_SCHED_H
+
+#include <linux/sched.h>
+#include <linux/tracepoint.h>
+
+DEFINE_TRACE(sched_kthread_stop,
+ TPPROTO(struct task_struct *t),
+ TPARGS(t));
+DEFINE_TRACE(sched_kthread_stop_ret,
+ TPPROTO(int ret),
+ TPARGS(ret));
+DEFINE_TRACE(sched_wait_task,
+ TPPROTO(struct rq *rq, struct task_struct *p),
+ TPARGS(rq, p));
+DEFINE_TRACE(sched_wakeup,
+ TPPROTO(struct rq *rq, struct task_struct *p),
+ TPARGS(rq, p));
+DEFINE_TRACE(sched_wakeup_new,
+ TPPROTO(struct rq *rq, struct task_struct *p),
+ TPARGS(rq, p));
+DEFINE_TRACE(sched_switch,
+ TPPROTO(struct rq *rq, struct task_struct *prev,
+ struct task_struct *next),
+ TPARGS(rq, prev, next));
+DEFINE_TRACE(sched_migrate_task,
+ TPPROTO(struct rq *rq, struct task_struct *p, int dest_cpu),
+ TPARGS(rq, p, dest_cpu));
+DEFINE_TRACE(sched_process_free,
+ TPPROTO(struct task_struct *p),
+ TPARGS(p));
+DEFINE_TRACE(sched_process_exit,
+ TPPROTO(struct task_struct *p),
+ TPARGS(p));
+DEFINE_TRACE(sched_process_wait,
+ TPPROTO(struct pid *pid),
+ TPARGS(pid));
+DEFINE_TRACE(sched_process_fork,
+ TPPROTO(struct task_struct *parent, struct task_struct *child),
+ TPARGS(parent, child));
+DEFINE_TRACE(sched_signal_send,
+ TPPROTO(int sig, struct task_struct *p),
+ TPARGS(sig, p));
+
+#endif
diff --git a/kernel/exit.c b/kernel/exit.c
index 85a83c8..7b71f87 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -47,6 +47,7 @@
#include <linux/blkdev.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/tracehook.h>
+#include <trace/sched.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -149,7 +150,10 @@
static void delayed_put_task_struct(struct rcu_head *rhp)
{
- put_task_struct(container_of(rhp, struct task_struct, rcu));
+ struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
+
+ trace_sched_process_free(tsk);
+ put_task_struct(tsk);
}
@@ -1074,6 +1078,8 @@
if (group_dead)
acct_process();
+ trace_sched_process_exit(tsk);
+
exit_sem(tsk);
exit_files(tsk);
exit_fs(tsk);
@@ -1675,6 +1681,8 @@
struct task_struct *tsk;
int retval;
+ trace_sched_process_wait(pid);
+
add_wait_queue(¤t->signal->wait_chldexit,&wait);
repeat:
/*
diff --git a/kernel/fork.c b/kernel/fork.c
index 30de644..cfaff92 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -58,6 +58,7 @@
#include <linux/tty.h>
#include <linux/proc_fs.h>
#include <linux/blkdev.h>
+#include <trace/sched.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1364,6 +1365,8 @@
if (!IS_ERR(p)) {
struct completion vfork;
+ trace_sched_process_fork(current, p);
+
nr = task_pid_vnr(p);
if (clone_flags & CLONE_PARENT_SETTID)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 96cff2f..50598e29 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -13,6 +13,7 @@
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <trace/sched.h>
#define KTHREAD_NICE_LEVEL (-5)
@@ -206,6 +207,8 @@
/* It could exit after stop_info.k set, but before wake_up_process. */
get_task_struct(k);
+ trace_sched_kthread_stop(k);
+
/* Must init completion *before* thread sees kthread_stop_info.k */
init_completion(&kthread_stop_info.done);
smp_wmb();
@@ -221,6 +224,8 @@
ret = kthread_stop_info.err;
mutex_unlock(&kthread_stop_lock);
+ trace_sched_kthread_stop_ret(ret);
+
return ret;
}
EXPORT_SYMBOL(kthread_stop);
diff --git a/kernel/sched.c b/kernel/sched.c
index 6f23059..3d1ad13 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -71,6 +71,7 @@
#include <linux/debugfs.h>
#include <linux/ctype.h>
#include <linux/ftrace.h>
+#include <trace/sched.h>
#include <asm/tlb.h>
#include <asm/irq_regs.h>
@@ -1936,6 +1937,7 @@
* just go back and repeat.
*/
rq = task_rq_lock(p, &flags);
+ trace_sched_wait_task(rq, p);
running = task_running(rq, p);
on_rq = p->se.on_rq;
ncsw = 0;
@@ -2297,9 +2299,7 @@
success = 1;
out_running:
- trace_mark(kernel_sched_wakeup,
- "pid %d state %ld ## rq %p task %p rq->curr %p",
- p->pid, p->state, rq, p, rq->curr);
+ trace_sched_wakeup(rq, p);
check_preempt_curr(rq, p, sync);
p->state = TASK_RUNNING;
@@ -2432,9 +2432,7 @@
p->sched_class->task_new(rq, p);
inc_nr_running(rq);
}
- trace_mark(kernel_sched_wakeup_new,
- "pid %d state %ld ## rq %p task %p rq->curr %p",
- p->pid, p->state, rq, p, rq->curr);
+ trace_sched_wakeup_new(rq, p);
check_preempt_curr(rq, p, 0);
#ifdef CONFIG_SMP
if (p->sched_class->task_wake_up)
@@ -2607,11 +2605,7 @@
struct mm_struct *mm, *oldmm;
prepare_task_switch(rq, prev, next);
- trace_mark(kernel_sched_schedule,
- "prev_pid %d next_pid %d prev_state %ld "
- "## rq %p prev %p next %p",
- prev->pid, next->pid, prev->state,
- rq, prev, next);
+ trace_sched_switch(rq, prev, next);
mm = next->mm;
oldmm = prev->active_mm;
/*
@@ -2851,6 +2845,7 @@
|| unlikely(!cpu_active(dest_cpu)))
goto out;
+ trace_sched_migrate_task(rq, p, dest_cpu);
/* force the process onto the specified CPU */
if (migrate_task(p, dest_cpu, &req)) {
/* Need to wait for migration thread (might exit: take ref). */
diff --git a/kernel/signal.c b/kernel/signal.c
index e661b01..bf40ecc 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -27,6 +27,7 @@
#include <linux/freezer.h>
#include <linux/pid_namespace.h>
#include <linux/nsproxy.h>
+#include <trace/sched.h>
#include <asm/param.h>
#include <asm/uaccess.h>
@@ -803,6 +804,8 @@
struct sigpending *pending;
struct sigqueue *q;
+ trace_sched_signal_send(sig, t);
+
assert_spin_locked(&t->sighand->siglock);
if (!prepare_signal(sig, t))
return 0;