linux-kernel - Re: [tip:tracing/urgent] tracing: Allocate the ftrace event profile buffer dynamically

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Message-ID: <20090919165247.GA9914@elte.hu>
Date:	Sat, 19 Sep 2009 18:52:47 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	lizf@...fujitsu.com, peterz@...radead.org, fweisbec@...il.com,
	tglx@...utronix.de, jbaron@...hat.com, mhiramat@...hat.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/urgent] tracing: Allocate the ftrace event
	profile buffer dynamically


* Steven Rostedt <rostedt@...dmis.org> wrote:

> On Sat, 2009-09-19 at 07:58 +0000, tip-bot for Frederic Weisbecker
> wrote:
> 
> > +/*
> > + * We can't use a size but a type in alloc_percpu()
> > + * So let's create a dummy type that matches the desired size
> > + */
> > +typedef struct {char buf[FTRACE_MAX_PROFILE_SIZE];} profile_buf_t;
> > +
> >  static int ftrace_profile_enable_event(struct ftrace_event_call *event)
> >  {
> > +	char *buf;
> > +	int ret;
> > +
> >  	if (atomic_inc_return(&event->profile_count))
> >  		return 0;
> >  
> > -	return event->profile_enable();
> > +	buf = (char *)alloc_percpu(profile_buf_t);
> > +	if (!buf)
> > +		return -ENOMEM;
> 
> Ingo,
> 
> Did you pull in the version that allocates a buffer for each event? I 
> thought Frederic made just a global per cpu buffer that all events can 
> use. The buffer is just a temporary storage that will be too big to 
> put on the stack.

Yeah - i had v1 briefly - then pulled in the later (v3) one.

	Ingo
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