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Message-ID: <20090217182045.GA28195@elte.hu>
Date: Tue, 17 Feb 2009 19:20:45 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/function-graph-tracer: trace the idle tasks
* Frederic Weisbecker <fweisbec@...il.com> wrote:
> When the function graph tracer is activated, it iterates over the task_list
> to allocate a stack to store the return addresses.
> But the per cpu idle tasks are not iterated by using do_each_thread / while_each_thread.
> So we have to iterate on them manually.
>
> This fixes somes weirdness in the traces and many losses of traces.
> Examples on two cpus:
>
> 0) Xorg-4287 | 2.906 us | }
> 0) Xorg-4287 | 3.965 us | }
> 0) Xorg-4287 | 5.302 us | }
> ------------------------------------------
> 0) Xorg-4287 => <idle>-0
> ------------------------------------------
>
> 0) <idle>-0 | 2.861 us | }
> 0) <idle>-0 | 0.526 us | set_normalized_timespec();
> 0) <idle>-0 | 7.201 us | }
> 0) <idle>-0 | 8.214 us | }
> 0) <idle>-0 | | clockevents_program_event() {
> 0) <idle>-0 | | lapic_next_event() {
> 0) <idle>-0 | 0.510 us | native_apic_mem_write();
> 0) <idle>-0 | 1.546 us | }
> 0) <idle>-0 | 2.583 us | }
> 0) <idle>-0 | + 12.435 us | }
> 0) <idle>-0 | + 13.470 us | }
> 0) <idle>-0 | 0.608 us | _spin_unlock_irqrestore();
> 0) <idle>-0 | + 23.270 us | }
> 0) <idle>-0 | + 24.336 us | }
> 0) <idle>-0 | + 25.417 us | }
> 0) <idle>-0 | 0.593 us | _spin_unlock();
> 0) <idle>-0 | + 41.869 us | }
> 0) <idle>-0 | + 42.906 us | }
> 0) <idle>-0 | + 95.035 us | }
> 0) <idle>-0 | 0.540 us | menu_reflect();
> 0) <idle>-0 | ! 100.404 us | }
> 0) <idle>-0 | 0.564 us | mce_idle_callback();
> 0) <idle>-0 | | enter_idle() {
> 0) <idle>-0 | 0.526 us | mce_idle_callback();
> 0) <idle>-0 | 1.757 us | }
> 0) <idle>-0 | | cpuidle_idle_call() {
> 0) <idle>-0 | | menu_select() {
> 0) <idle>-0 | 0.525 us | pm_qos_requirement();
> 0) <idle>-0 | 0.518 us | tick_nohz_get_sleep_length();
> 0) <idle>-0 | 2.621 us | }
> [...]
> 1) <idle>-0 | 0.518 us | touch_softlockup_watchdog();
> 1) <idle>-0 | + 14.355 us | }
> 1) <idle>-0 | + 22.840 us | }
> 1) <idle>-0 | + 25.949 us | }
> 1) <idle>-0 | | handle_irq() {
> 1) <idle>-0 | 0.511 us | irq_to_desc();
> 1) <idle>-0 | | handle_edge_irq() {
> 1) <idle>-0 | 0.638 us | _spin_lock();
> 1) <idle>-0 | | ack_apic_edge() {
> 1) <idle>-0 | 0.510 us | irq_to_desc();
> 1) <idle>-0 | | move_native_irq() {
> 1) <idle>-0 | 0.510 us | irq_to_desc();
> 1) <idle>-0 | 1.532 us | }
> 1) <idle>-0 | 0.511 us | native_apic_mem_write();
> ------------------------------------------
> 1) <idle>-0 => cat-5073
> ------------------------------------------
>
> 1) cat-5073 | 3.731 us | }
> 1) cat-5073 | | run_local_timers() {
> 1) cat-5073 | 0.533 us | hrtimer_run_queues();
> 1) cat-5073 | | raise_softirq() {
> 1) cat-5073 | | __raise_softirq_irqoff() {
> 1) cat-5073 | | /* nr: 1 */
> 1) cat-5073 | 2.718 us | }
> 1) cat-5073 | 3.814 us | }
>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
> kernel/trace/ftrace.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
Applied to tip:tracing/urgent, thanks Frederic!
Ingo
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