Currently we only have one sched_switch trace event
for task switching, which is generated very early during
task switch. When we try to monitor per-container perf
events, this is not what we expect.
For example, we have a process A which is in the cgroup
we monitor, and process B which isn't, when kernel switches
from B to A, the sched_switch event is not recorded for this
cgroup since it belongs to B (current process is still B
util we finish the switch), but we require this event to
signal that process A in this cgroup gets scheduled. This is
crucial for calculating schedule latency (like `perf sched`).
Ideally, we need to split the sched_switch event into two:
sched_in event before we perform the switch, and sched_out
event after we perform the switch. However, for compatibility,
we can not change the sched_switch event. So before we have
trace event alias, we can just reuse sched_switch and introduce
sched_switch_post event instead.
Suggested-by: Steven Rostedt <rost...@goodmis.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
Signed-off-by: Cong Wang <cw...@twopensource.com>
---
include/trace/events/sched.h | 43 ++++++++++++++++++++++++++++++++++++++++++-
kernel/sched/core.c | 1 +
2 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index d57a575..4bc7db5 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -112,7 +112,9 @@ static inline long __trace_sched_switch_state(struct
task_struct *p)
#endif /* CREATE_TRACE_POINTS */
/*
- * Tracepoint for task switches, performed by the scheduler:
+ * Tracepoints for task switches, performed by the scheduler:
+ * sched_switch is performed before task switch,
+ * sched_switch_post is performed after task switch.
*/
TRACE_EVENT(sched_switch,
@@ -153,6 +155,45 @@ TRACE_EVENT(sched_switch,
__entry->next_comm, __entry->next_pid, __entry->next_prio)
);
+TRACE_EVENT(sched_switch_post,
+
+ TP_PROTO(struct task_struct *prev,
+ struct task_struct *curr),
+
+ TP_ARGS(prev, curr),
+
+ TP_STRUCT__entry(
+ __array( char, prev_comm, TASK_COMM_LEN )
+ __field( pid_t, prev_pid )
+ __field( int, prev_prio )
+ __field( long, prev_state )
+ __array( char, curr_comm, TASK_COMM_LEN )
+ __field( pid_t, curr_pid )
+ __field( int, curr_prio )
+ ),
+
+ TP_fast_assign(
+ memcpy(__entry->curr_comm, curr->comm, TASK_COMM_LEN);
+ __entry->prev_pid = prev->pid;
+ __entry->prev_prio = prev->prio;
+ __entry->prev_state = __trace_sched_switch_state(prev);
+ memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
+ __entry->curr_pid = curr->pid;
+ __entry->curr_prio = curr->prio;
+ ),
+
+ TP_printk("prev_comm=%s prev_pid=%d prev_prio=%d prev_state=%s%s ==>
curr_comm=%s curr_pid=%d curr_prio=%d",
+ __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
+ __entry->prev_state & (TASK_STATE_MAX-1) ?
+ __print_flags(__entry->prev_state & (TASK_STATE_MAX-1), "|",
+ { 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },
+ { 16, "Z" }, { 32, "X" }, { 64, "x" },
+ { 128, "K" }, { 256, "W" }, { 512, "P" },
+ { 1024, "N" }) : "R",
+ __entry->prev_state & TASK_STATE_MAX ? "+" : "",
+ __entry->curr_comm, __entry->curr_pid, __entry->curr_prio)
+);
+
/*
* Tracepoint for a task being migrated:
*/
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 78b4bad10..3c74cf4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2490,6 +2490,7 @@ static struct rq *finish_task_switch(struct task_struct
*prev)
}
tick_nohz_task_switch(current);
+ trace_sched_switch_post(prev, current);
return rq;
}
--
1.8.3.1
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