linux-kernel - Re: [PATCH 4/5 v3] tracing/core: drop the old ftrace_printk implementation in favour of ftrace

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Message-ID: <20090306170222.GA11285@elte.hu>
Date:	Fri, 6 Mar 2009 18:02:22 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 4/5 v3] tracing/core: drop the old ftrace_printk
	implementation in favour of ftrace_bprintk


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

> 
> 
> On Fri, 6 Mar 2009, Frederic Weisbecker wrote:
> 
> > Impact: faster and lighter tracing
> > 
> > Now that we have ftrace_bprintk() which is faster and consume lesser
> > memory than ftrace_printk() and has the same purpose, we can now drop
> > the old implementation in favour of the binary one from ftrace_bprintk(),
> > which means we move all the implementation of ftrace_bprintk() to
> > ftrace_printk(), so the Api doesn't change except that we must now use
> > trace_seq_bprintk() to print the TRACE_PRINT entries.
> > 
> > Some changes result of this:
> > 
> > - Previously, ftrace_bprintk depended of a single tracer and couldn't
> >   work without. This tracer has been dropped and the whole implementation
> >   of ftrace_printk() (like the module formats management) is now integrated
> >   in the tracing core (comes with CONFIG_TRACING), though we keep the file
> >   trace_printk (previously trace_bprintk.c) where we can find the module
> >   management. Thus we don't overflow trace.c
> > 
> > - changes some parts to use trace_seq_bprintk() to print TRACE_PRINT entries.
> > 
> > - change a bit ftrace_printk/ftrace_vprintk macros to support non-builtin formats
> >   constants, and fix 'const' qualifiers warnings. But this is all transparent for
> >   developers.
> > 
> > - etc...
> > 
> > V2:
> > 
> > - Rebase against last changes
> > - Fix mispell on the changelog
> > 
> > V3:
> > 
> > - Rebase against last changes (moving ftrace_printk() to kernel.h)
> > 
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> 
> Very nice Frederic!
> 
> For some reason I'm still missing patch 1. Perhaps it decided to take the
> scenic route ;-)
> 
> > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > index 0f5077f..6140922 100644
> > --- a/kernel/trace/trace.h
> > +++ b/kernel/trace/trace.h
> > @@ -20,7 +20,6 @@ enum trace_type {
> >  	TRACE_WAKE,
> >  	TRACE_STACK,
> >  	TRACE_PRINT,
> > -	TRACE_BPRINTK,
> >  	TRACE_SPECIAL,
> >  	TRACE_MMIO_RW,
> >  	TRACE_MMIO_MAP,
> > @@ -120,16 +119,10 @@ struct userstack_entry {
> >   */
> >  struct print_entry {
> >  	struct trace_entry	ent;
> > -	unsigned long		ip;
> > +	unsigned long 		ip;
> >  	int			depth;
> > -	char			buf[];
> > -};
> > -
> 
> 
> Note, this is going to break my recent patch that exports the 
> internal ftrace events. That's OK, I'll fix it after Ingo 
> pulls it in.
> 
> Ingo,
> 
> Would you prefer that I pull these patches in and then fix the 
> code, and let you pull it from me?

i've put them into a separate branch forked off 
tip:tracing/ftrace: tip:tracing/printk. The two vsprintf patches 
are in tip:core/printk and merged into tracing/ftrace.

You can thus apply your current enhancements without any 
interaction with me - and merge tracing/printk into the 
tip:tracing/ftrace branch on your own schedule, ok?

	Ingo
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