From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>, Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
SystemTap <systemtap@sourceware.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: systemtap broken by removal of register_timer_hook
Date: Mon, 06 May 2013 23:12:00 -0000 [thread overview]
Message-ID: <20130506231237.GB1225@somewhere> (raw)
In-Reply-To: <20130430172720.GA21499@redhat.com>
On Tue, Apr 30, 2013 at 01:27:20PM -0400, Frank Ch. Eigler wrote:
> Hi -
>
> > [...] How about creating trace_tick() in
> > include/trace/events/timer.h and call it from tick_periodic() and
> > tick_sched_handle(). [...]
>
> Like this?
>
>
> From facee64445c0dcc717e99c474c5c7dcdd31b9a74 Mon Sep 17 00:00:00 2001
> From: "Frank Ch. Eigler" <fche@redhat.com>
> Date: Wed, 3 Apr 2013 10:35:21 -0400
> Subject: [PATCH] profiling: add tick tracepoint
I'd rather entitle "timer: Add tick tracepoint", as it doesn't depend
on the profiling stuff.
>
> Commit ba6fdda4 removed the timer_hook mechanism for modules to listen
> to profiling timer ticks (without having to set up more complicated
> perf mechanisms). To reduce the impact on out-of-tree users such as
> systemtap, a TRACE_EVENT-flavoured tracepoint is added in its place,
> invoked right beside profile_tick() in kernel/time/tick-*.c.
> Tested with perf and systemtap.
>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Signed-off-by: Frank Ch. Eigler <fche@redhat.com>
> ---
> include/trace/events/timer.h | 20 ++++++++++++++++++++
> kernel/time/tick-common.c | 2 ++
> kernel/time/tick-sched.c | 2 ++
> 3 files changed, 24 insertions(+)
>
> diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
> index 425bcfe..ec4c2d0 100644
> --- a/include/trace/events/timer.h
> +++ b/include/trace/events/timer.h
> @@ -323,6 +323,26 @@ TRACE_EVENT(itimer_expire,
> (int) __entry->pid, (unsigned long long)__entry->now)
> );
>
> +
> +struct pt_regs;
> +
> +/**
> + * tick - called when the profiling timer ticks
> + * @regs: pointer to struct pt_regs*
> + */
> +TRACE_EVENT(tick,
> + TP_PROTO(struct pt_regs *regs),
> + TP_ARGS(regs),
> + TP_STRUCT__entry(
> + __field( struct pt_regs*, regs )
I doubt the pointer to the regs is interesting in userland.
How about "void *ip" instead?
> + ),
> + TP_fast_assign(
> + __entry->regs = regs;
> + ),
> + TP_printk("ip=%p", (void *) instruction_pointer(__entry->regs))
> +);
> +
> +
> #endif /* _TRACE_TIMER_H */
>
> /* This part must be outside protection */
> diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
> index b1600a6..5f4227f 100644
> --- a/kernel/time/tick-common.c
> +++ b/kernel/time/tick-common.c
> @@ -18,6 +18,7 @@
> #include <linux/percpu.h>
> #include <linux/profile.h>
> #include <linux/sched.h>
> +#include <trace/events/timer.h>
>
> #include <asm/irq_regs.h>
>
> @@ -74,6 +75,7 @@ static void tick_periodic(int cpu)
>
> update_process_times(user_mode(get_irq_regs()));
> profile_tick(CPU_PROFILING);
> + trace_tick(get_irq_regs());
I suggest storing get_irq_regs() in a local variable so the function
doesn't fetch it twice from whatever per cpu area.
> }
>
> /*
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index a19a399..447be56 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -21,6 +21,7 @@
> #include <linux/sched.h>
> #include <linux/module.h>
> #include <linux/irq_work.h>
> +#include <trace/events/timer.h>
>
> #include <asm/irq_regs.h>
>
> @@ -140,6 +141,7 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
> #endif
> update_process_times(user_mode(regs));
> profile_tick(CPU_PROFILING);
> + trace_tick(get_irq_regs());
And here you can reuse the regs parameter.
> }
>
> /*
> --
> 1.8.2
>
next prev parent reply other threads:[~2013-05-06 23:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-03 7:50 Mel Gorman
2013-04-03 11:01 ` Frederic Weisbecker
[not found] ` <CAFTL4hyYezB2ZxM-GJ70VoxOeRSG64V6u+nX2hTuhF30R-GdPg__32168.962484184$1364986928$gmane$org@mail.gmail.com>
2013-04-03 12:29 ` Frank Ch. Eigler
2013-04-03 12:50 ` Frederic Weisbecker
2013-04-03 14:44 ` Frank Ch. Eigler
2013-04-03 18:38 ` Josh Stone
2013-04-04 12:46 ` Frederic Weisbecker
2013-04-19 14:47 ` Frank Ch. Eigler
2013-04-30 0:19 ` Frederic Weisbecker
2013-04-30 17:27 ` Frank Ch. Eigler
2013-05-06 23:12 ` Frederic Weisbecker [this message]
2013-04-10 11:25 ` Ingo Molnar
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