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Message-ID: <20120521080626.GA3591@m.brq.redhat.com>
Date: Mon, 21 May 2012 10:06:26 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: acme@...hat.com, a.p.zijlstra@...llo.nl, mingo@...e.hu,
paulus@...ba.org, cjashfor@...ux.vnet.ibm.com, fweisbec@...il.com
Cc: linux-kernel@...r.kernel.org, eranian@...gle.com
Subject: [RFC][BUG] Revert "sched, perf: Use a single callback into the
scheduler"
hi,
Arnaldo an I were hunting why test__PERF_RECORD stop work recently.
It seems that following commit is the culprit:
sched, perf: Use a single callback into the scheduler
commit cb04ff9ac424d0e689d9b612e9f73cb443ab4b7e
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Tue May 8 18:56:04 2012 +0200
the reason seems to be following:
- before commit this change was introduced, the process switch worked
like this (wrt to perf event schedule):
schedule (prev, next)
- schedule out all perf events for prev
- switch to next
- schedule in all perf events for current (next)
- after the commit, the process switch looks like:
schedule (prev, next)
- schedule out all perf events for prev
- schedule in all perf events for (next)
- switch to next
The problem is, that after we schedule perf events in, the pmu is
enabled and we can receive events even before we make the switch
to next - so "current" still being prev process (event SAMPLE data
are filled based on the value of the "current" process).
Thats exactly what we see for test__PERF_RECORD test. We receive
SAMPLES with PID of the process that our tracee is scheduled from.
Most of the time it's parent, sometimes idle (0).
I tried to keep the current code and add a new hook from finish_task_switch
to enable related PMUs for task.. but I'm getting following warning:
WARNING: at arch/x86/kernel/cpu/perf_event.c:1054 x86_pmu_start+0x133/0x140()
which I haven't figured out yet... also I'm not sure if thats even
right thing to do ;)
thoughts? thanks,
jirka
---
This reverts commit cb04ff9ac424d0e689d9b612e9f73cb443ab4b7e.
---
include/linux/perf_event.h | 24 ++++++++++++++++++------
kernel/events/core.c | 14 ++++----------
kernel/sched/core.c | 9 ++++++++-
3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8adf70e..f325786 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1084,8 +1084,10 @@ extern void perf_pmu_unregister(struct pmu *pmu);
extern int perf_num_counters(void);
extern const char *perf_pmu_name(void);
-extern void __perf_event_task_sched(struct task_struct *prev,
- struct task_struct *next);
+extern void __perf_event_task_sched_in(struct task_struct *prev,
+ struct task_struct *task);
+extern void __perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next);
extern int perf_event_init_task(struct task_struct *child);
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
@@ -1205,13 +1207,20 @@ perf_sw_event(u32 event_id, u64 nr, struct pt_regs *regs, u64 addr)
extern struct static_key_deferred perf_sched_events;
-static inline void perf_event_task_sched(struct task_struct *prev,
+static inline void perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task)
{
+ if (static_key_false(&perf_sched_events.key))
+ __perf_event_task_sched_in(prev, task);
+}
+
+static inline void perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next)
+{
perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, NULL, 0);
if (static_key_false(&perf_sched_events.key))
- __perf_event_task_sched(prev, task);
+ __perf_event_task_sched_out(prev, next);
}
extern void perf_event_mmap(struct vm_area_struct *vma);
@@ -1286,8 +1295,11 @@ extern void perf_event_disable(struct perf_event *event);
extern void perf_event_task_tick(void);
#else
static inline void
-perf_event_task_sched(struct task_struct *prev,
- struct task_struct *task) { }
+perf_event_task_sched_in(struct task_struct *prev,
+ struct task_struct *task) { }
+static inline void
+perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next) { }
static inline int perf_event_init_task(struct task_struct *child) { return 0; }
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 91a4459..5b06cbb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2039,8 +2039,8 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
* accessing the event control register. If a NMI hits, then it will
* not restart the event.
*/
-static void __perf_event_task_sched_out(struct task_struct *task,
- struct task_struct *next)
+void __perf_event_task_sched_out(struct task_struct *task,
+ struct task_struct *next)
{
int ctxn;
@@ -2279,8 +2279,8 @@ static void perf_branch_stack_sched_in(struct task_struct *prev,
* accessing the event control register. If a NMI hits, then it will
* keep the event running.
*/
-static void __perf_event_task_sched_in(struct task_struct *prev,
- struct task_struct *task)
+void __perf_event_task_sched_in(struct task_struct *prev,
+ struct task_struct *task)
{
struct perf_event_context *ctx;
int ctxn;
@@ -2305,12 +2305,6 @@ static void __perf_event_task_sched_in(struct task_struct *prev,
perf_branch_stack_sched_in(prev, task);
}
-void __perf_event_task_sched(struct task_struct *prev, struct task_struct *next)
-{
- __perf_event_task_sched_out(prev, next);
- __perf_event_task_sched_in(prev, next);
-}
-
static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
u64 frequency = event->attr.sample_freq;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 18eed17..90c2427 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1913,7 +1913,7 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
sched_info_switch(prev, next);
- perf_event_task_sched(prev, next);
+ perf_event_task_sched_out(prev, next);
fire_sched_out_preempt_notifiers(prev, next);
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
@@ -1956,6 +1956,13 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
*/
prev_state = prev->state;
finish_arch_switch(prev);
+#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
+ local_irq_disable();
+#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
+ perf_event_task_sched_in(prev, current);
+#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
+ local_irq_enable();
+#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
finish_lock_switch(rq, prev);
finish_arch_post_lock_switch();
--
1.7.7.6
--
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