From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755920Ab2EUIG4 (ORCPT ); Mon, 21 May 2012 04:06:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21637 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751746Ab2EUIGx (ORCPT ); Mon, 21 May 2012 04:06:53 -0400 Date: Mon, 21 May 2012 10:06:26 +0200 From: Jiri Olsa To: acme@redhat.com, a.p.zijlstra@chello.nl, mingo@elte.hu, paulus@samba.org, cjashfor@linux.vnet.ibm.com, fweisbec@gmail.com Cc: linux-kernel@vger.kernel.org, eranian@google.com Subject: [RFC][BUG] Revert "sched, perf: Use a single callback into the scheduler" Message-ID: <20120521080626.GA3591@m.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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