linux-kernel - Re: [PATCH 3/3] tracing: add flag output for kmem events

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Date:	Fri, 15 May 2009 17:50:44 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 3/3] tracing: add flag output for kmem events


On Fri, 15 May 2009, Frederic Weisbecker wrote:

> On Fri, May 15, 2009 at 05:03:45PM -0400, Steven Rostedt wrote:
> > From: Steven Rostedt <srostedt@...hat.com>
> > 
> > This patch changes the output for gfp_flags from being a simple hex value
> > to the actual names.
> > 
> >   gfp_flags=GFP_ATOMIC  instead of gfp_flags=00000020
> > 
> > And even
> > 
> >   gfp_flags=GFP_KERNEL instead of gfp_flags=000000d0
> > 
> > [ Impact: more human readable output from tracer ]
> > 
> > Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> 
> 
> Nice!
> 
> 
> > ---
> >  include/trace/events/kmem.h |   43 +++++++++++++++++++++++++++++++++++--------
> >  1 files changed, 35 insertions(+), 8 deletions(-)
> > 
> > diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
> > index c22c42f..9b3886b 100644
> > --- a/include/trace/events/kmem.h
> > +++ b/include/trace/events/kmem.h
> > @@ -7,6 +7,33 @@
> >  #undef TRACE_SYSTEM
> >  #define TRACE_SYSTEM kmem
> >  
> > +#define show_gfp_flags(flags)						\
> > +	(flags) ? __print_flags(flags, "|",				\
> > +	(unsigned long)GFP_KERNEL,		"GFP_KERNEL",		\
> > +	(unsigned long)GFP_NOFS,		"GFP_NOFS",		\
> > +	(unsigned long)GFP_TEMPORARY,		"GFP_TEMPORARY",	\
> > +	(unsigned long)GFP_USER,		"GFP_USER",		\
> 
> 
> Because you clear the mask value after finding out a matching mask
> string, you should sort the masks from the highest number of bits
> to the lowest.
> 
> GFP_USER should be placed before GFP_KERNEL otherwise it will always be
> eaten.
> Instead of GFP_USER, you will get:
> 
> GFP_KERNEL | __GFP_HARDWALL

Ug, I was thinking the code only printed the mask if the mask matched 
fully.

> 
> 
> > +	(unsigned long)GFP_HIGHUSER,		"GFP_HIGHUSER",		\
> 
> 
> Ditto, it should be placed before GFP_USER otherwise you will get:
> 
> GFP_USER | __GFP_HIGHMEM
> 
> 
> > +	(unsigned long)GFP_HIGHUSER_MOVABLE,	"GFP_HIGHUSER_MOVABLE",	\
> 
> And this one before HIGH_USER otherwise:
> 
> GFP_HIGHUSER__GFP_MOVABLE

Anyway, I thought I did sort it out, but I did not realize that some masks 
have masks within. I need more sleep.

Will fix in take two. Still waiting for comments from the MM folks.

-- Steve
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