linux-kernel - Re: [RFC PATCH v2 1/5] irq: add tracepoint to softirq

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Date:	Thu, 24 Jun 2010 15:15:14 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Koki Sanagi <sanagi.koki@...fujitsu.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	scott.a.mcmillan@...el.com, kaneshige.kenji@...fujitsu.com,
	izumi.taku@...fujitsu.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/5] irq: add tracepoint to softirq_raise

Hi Koki,

Your subject says 1/5 but I do not see any other patches.


On Thu, 2010-06-24 at 17:16 +0900, Koki Sanagi wrote:
> This patch adds a tracepoint to raising of softirq.
> This is useful if you want to detect which hard interrupt raise softirq
> and lets you know a time between raising softirq and performing softirq.
> Combinating with other tracepoint, it lets us know a process of packets
> (See patch 0/5).
> 
>           <idle>-0     [001] 241229.957184: softirq_raise: vec=3 [action=NET_RX]
>           <idle>-0     [000] 241229.993399: softirq_raise: vec=1 [action=TIMER]
>           <idle>-0     [000] 241229.993400: softirq_raise: vec=9 [action=RCU]
> 
> This is a same patch Lai Jiangshan submitted.
> http://marc.info/?l=linux-kernel&m=126026122728732&w=2
> 
> Signed-off-by: Koki Sanagi <sanagi.koki@...fujitsu.com>
> ---
>  include/linux/interrupt.h  |    8 +++++++-
>  include/trace/events/irq.h |   34 +++++++++++++++++++++++++++++++---
>  2 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index c233113..1cb5726 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -18,6 +18,7 @@
>  #include <asm/atomic.h>
>  #include <asm/ptrace.h>
>  #include <asm/system.h>
> +#include <trace/events/irq.h>
>  
>  /*
>   * These correspond to the IORESOURCE_IRQ_* defines in
> @@ -402,7 +403,12 @@ asmlinkage void do_softirq(void);
>  asmlinkage void __do_softirq(void);
>  extern void open_softirq(int nr, void (*action)(struct softirq_action *));
>  extern void softirq_init(void);
> -#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)
> +static inline void __raise_softirq_irqoff(unsigned int nr)
> +{
> +	trace_softirq_raise(nr);
> +	or_softirq_pending(1UL << nr);
> +}
> +
>  extern void raise_softirq_irqoff(unsigned int nr);
>  extern void raise_softirq(unsigned int nr);
>  extern void wakeup_softirqd(void);
> diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
> index 0e4cfb6..7cb7435 100644
> --- a/include/trace/events/irq.h
> +++ b/include/trace/events/irq.h
> @@ -5,7 +5,9 @@
>  #define _TRACE_IRQ_H
>  
>  #include <linux/tracepoint.h>
> -#include <linux/interrupt.h>
> +
> +struct irqaction;
> +struct softirq_action;
>  
>  #define softirq_name(sirq) { sirq##_SOFTIRQ, #sirq }
>  #define show_softirq_name(val)				\
> @@ -82,6 +84,32 @@ TRACE_EVENT(irq_handler_exit,
>  		  __entry->irq, __entry->ret ? "handled" : "unhandled")
>  );
>  
> +/**
> + * softirq_raise - called immediately when a softirq is raised
> + * @nr: softirq vector number
> + *
> + * Tracepoint for tracing when softirq action is raised.
> + * Also, when used in combination with the softirq_entry tracepoint
> + * we can determine the softirq raise latency.
> + */
> +TRACE_EVENT(softirq_raise,
> +
> +	TP_PROTO(unsigned int nr),
> +
> +	TP_ARGS(nr),
> +
> +	TP_STRUCT__entry(
> +		__field(	unsigned int,	vec	)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->vec	= nr;
> +	),
> +
> +	TP_printk("vec=%d [action=%s]", __entry->vec,
> +		show_softirq_name(__entry->vec))

Hmm, is there a way to reuse a DECLARE_EVENT_CLASS here?

> +);
> +
>  DECLARE_EVENT_CLASS(softirq,
>  
>  	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
> @@ -89,11 +117,11 @@ DECLARE_EVENT_CLASS(softirq,
>  	TP_ARGS(h, vec),
>  
>  	TP_STRUCT__entry(
> -		__field(	int,	vec			)
> +		__field(	unsigned int,	vec	)
>  	),
>  
>  	TP_fast_assign(
> -		__entry->vec = (int)(h - vec);
> +		__entry->vec = (unsigned int)(h - vec);

Just curious, did you see the original as a bug?

-- Steve

>  	),
>  
>  	TP_printk("vec=%d [action=%s]", __entry->vec,


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