Re: [RFC] [PATCH 0/5] Teach perf tool to profile sleep times (V4)
From: Peter Zijlstra
Date: Mon Jun 04 2012 - 08:41:11 EST
On Mon, 2012-06-04 at 12:09 +0400, Andrew Vagin wrote:
> This series resolves a problem with events filtering and non-root users.
> Before I tried to use sched_stat* events, but it occurs in a context of
> another task. For this case logic of perf_event_context* doesn't work.
>
> This series adds one more event sched:sched_switch_finish, it's sent
> when a task starts executing on a cpu. When a task goes out from cpu,
> sched:sched_switch is sent.
>
> The time difference between sched_switch and sched_switch_finish is a time
> when a task wasn't being executed on a cpu.
So I really don't like this stuff either.. :-)
Mostly because it adds very similar stuff to what's already there and
then doesn't try and consolidate things.
And partly because you're measuring the 'wrong' thing, the delay between
sched-out and sched-in includes a number of things, only one part of
that is the delay due to blocking.
And as a result you need that hideous prev_state crap.
Would something like the below work?
The one thing I'm not entirely sure of is if this is a sekjoerity issue
or not.. anybody? I would think a task was entitled to know who woke it
and wherefrom etc..
---
include/linux/ftrace_event.h | 5 +++--
include/linux/perf_event.h | 3 ++-
include/trace/events/sched.h | 4 ++++
include/trace/ftrace.h | 6 +++++-
kernel/events/core.c | 19 ++++++++++++++++++-
kernel/sched/core.c | 2 +-
6 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 176a939..55b96e3 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -303,9 +303,10 @@ extern void *perf_trace_buf_prepare(int size, unsigned short type,
static inline void
perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
- u64 count, struct pt_regs *regs, void *head)
+ u64 count, struct pt_regs *regs, void *head,
+ struct task_struct *task)
{
- perf_tp_event(addr, count, raw_data, size, regs, head, rctx);
+ perf_tp_event(addr, count, raw_data, size, regs, head, rctx, task);
}
#endif
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f325786..a3d7b90 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1269,7 +1269,8 @@ static inline bool perf_paranoid_kernel(void)
extern void perf_event_init(void);
extern void perf_tp_event(u64 addr, u64 count, void *record,
int entry_size, struct pt_regs *regs,
- struct hlist_head *head, int rctx);
+ struct hlist_head *head, int rctx,
+ struct task_struct *task);
extern void perf_bp_event(struct perf_event *event, void *data);
#ifndef perf_misc_flags
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index ea7a203..31da561 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -75,6 +75,10 @@ DECLARE_EVENT_CLASS(sched_wakeup_template,
__entry->target_cpu = task_cpu(p);
),
+ TP_perf_assign(
+ __perf_task(p);
+ ),
+
TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d",
__entry->comm, __entry->pid, __entry->prio,
__entry->success, __entry->target_cpu)
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 7697249..db14daf 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -711,6 +711,9 @@ __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
#undef __perf_count
#define __perf_count(c) __count = (c)
+#undef __perf_task
+#define __perf_task(t) __task = (t)
+
#undef TP_perf_assign
#define TP_perf_assign(args...) args
@@ -724,6 +727,7 @@ perf_trace_##call(void *__data, proto) \
struct ftrace_raw_##call *entry; \
struct pt_regs __regs; \
u64 __addr = 0, __count = 1; \
+ struct task_struct *__task = NULL; \
struct hlist_head *head; \
int __entry_size; \
int __data_size; \
@@ -751,7 +755,7 @@ perf_trace_##call(void *__data, proto) \
\
head = this_cpu_ptr(event_call->perf_events); \
perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \
- __count, &__regs, head); \
+ __count, &__regs, head, __task); \
}
/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5b06cbb..cb84cbd6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5204,7 +5204,8 @@ static int perf_tp_event_match(struct perf_event *event,
}
void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
- struct pt_regs *regs, struct hlist_head *head, int rctx)
+ struct pt_regs *regs, struct hlist_head *head, int rctx,
+ struct task_struct *task)
{
struct perf_sample_data data;
struct perf_event *event;
@@ -5223,6 +5224,22 @@ void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
perf_swevent_event(event, count, &data, regs);
}
+ /*
+ * If we got specified a target task, also iterate its context and
+ * deliver this event there too.
+ */
+ if (task) {
+ struct perf_event_context *ctx;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(task->perf_event_ctxp[perf_sw_context]);
+ list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+ if (perf_tp_event_match(event, &data, regs))
+ perf_swevent_event(event, count, &data, regs);
+ }
+ rcu_read_unlock();
+ }
+
perf_swevent_put_recursion_context(rctx);
}
EXPORT_SYMBOL_GPL(perf_tp_event);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 420e118..8ac193c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1912,11 +1912,11 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
sched_info_switch(prev, next);
+ trace_sched_switch(prev, next); /* before we flip the trace context */
perf_event_task_sched_out(prev, next);
fire_sched_out_preempt_notifiers(prev, next);
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
- trace_sched_switch(prev, next);
}
/**
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