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Date: Tue, 21 Oct 2008 14:47:19 +0200
From: "Frédéric Weisbecker" <fweisbec@...il.com>
To: "Ingo Molnar" <mingo@...e.hu>
Cc: "Arjan van de Ven" <arjan@...ux.intel.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] tracing/fastboot: Make the boot tracer use the cpu_clock
2008/10/11 Frederic Weisbecker <fweisbec@...il.com>:
> Make the boot tracer use the cpu_clock() rather than the ktime
> API. This way we will be able to unify the time capture with
> the sched_switch tracer.
> Also delete the duration attribute which is not needed and can be
> retrieved at print time.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>
> ---
> include/linux/ftrace.h | 5 ++---
> init/main.c | 25 ++++++++++++++++++-------
> kernel/trace/trace_boot.c | 18 ++++++++++--------
> 3 files changed, 30 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 135a33f..36b570b 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -222,9 +222,8 @@ struct boot_trace {
> pid_t caller;
> char func[KSYM_NAME_LEN];
> int result;
> - unsigned long long duration;
> - ktime_t calltime;
> - ktime_t rettime;
> + unsigned long long calltime;
> + unsigned long long rettime;
> };
>
> #ifdef CONFIG_BOOT_TRACER
> diff --git a/init/main.c b/init/main.c
> index 98c05aa..bf13013 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -721,27 +721,38 @@ __setup("initcall_debug", initcall_debug_setup);
> int do_one_initcall(initcall_t fn)
> {
> int count = preempt_count();
> - ktime_t delta;
> + ktime_t delta, t0, t1;
> char msgbuf[64];
> + unsigned long long duration;
> struct boot_trace it;
>
> if (initcall_debug) {
> + long cpu;
> it.caller = task_pid_nr(current);
> printk("calling %pF @ %i\n", fn, it.caller);
> - it.calltime = ktime_get();
> + t0 = ktime_get();
> + preempt_disable();
> + cpu = raw_smp_processor_id();
> + it.calltime = cpu_clock(cpu);
> + preempt_enable();
> enable_boot_trace();
> }
>
> it.result = fn();
>
> if (initcall_debug) {
> - it.rettime = ktime_get();
> - delta = ktime_sub(it.rettime, it.calltime);
> - it.duration = (unsigned long long) delta.tv64 >> 20;
> + long cpu;
> + disable_boot_trace();
> + t1 = ktime_get();
> + preempt_disable();
> + cpu = raw_smp_processor_id();
> + it.rettime = cpu_clock(cpu);
> + preempt_enable();
> + delta = ktime_sub(t1, t0);
> + duration = (unsigned long long) delta.tv64 >> 20;
> printk("initcall %pF returned %d after %Ld msecs\n", fn,
> - it.result, it.duration);
> + it.result, duration);
> trace_boot(&it, fn);
> - disable_boot_trace();
> }
>
> msgbuf[0] = 0;
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index bd5046c..20d326b 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -68,22 +68,24 @@ static enum print_line_t initcall_print_line(struct trace_iterator *iter)
> struct trace_boot *field = (struct trace_boot *)entry;
> struct boot_trace *it = &field->initcall;
> struct trace_seq *s = &iter->seq;
> - struct timespec calltime = ktime_to_timespec(it->calltime);
> - struct timespec rettime = ktime_to_timespec(it->rettime);
> + unsigned long sec, nsec_rem;
> + unsigned long long duration = it->rettime - it->calltime;
>
> if (entry->type == TRACE_BOOT) {
> + nsec_rem = do_div(it->calltime, 1000000000);
> + sec = (unsigned long) it->calltime;
> ret = trace_seq_printf(s, "[%5ld.%09ld] calling %s @ %i\n",
> - calltime.tv_sec,
> - calltime.tv_nsec,
> - it->func, it->caller);
> + sec, nsec_rem, it->func, it->caller);
> if (!ret)
> return TRACE_TYPE_PARTIAL_LINE;
>
> + nsec_rem = do_div(it->rettime, 1000000000);
> + sec = (unsigned long) it->rettime;
> + do_div(duration, 1000);
> ret = trace_seq_printf(s, "[%5ld.%09ld] initcall %s "
> "returned %d after %lld msecs\n",
> - rettime.tv_sec,
> - rettime.tv_nsec,
> - it->func, it->result, it->duration);
> + sec, nsec_rem, it->func, it->result,
> + duration);
>
> if (!ret)
> return TRACE_TYPE_PARTIAL_LINE;
>
Please just ignore this patch. I think I will change a bit the design
of the boot tracer by sending
two types of entries: the call and the return. With this new approach,
I will be able to use the internal
timestamp of the ring buffer and stay consistent with the same used
for sched switch entries.
Thanks.
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