linux-kernel - Re: [PATCH 4/5] kmemtrace: SLUB hooks.

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Message-ID: <20080812152548.GA5973@localhost>
Date:	Tue, 12 Aug 2008 18:25:49 +0300
From:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	mathieu.desnoyers@...ymtl.ca, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, rdunlap@...otime.net,
	mpm@...enic.com, rostedt@...dmis.org, tglx@...utronix.de
Subject: Re: [PATCH 4/5] kmemtrace: SLUB hooks.

On Mon, Aug 11, 2008 at 05:09:34PM +0300, Pekka Enberg wrote:
> On Mon, 2008-08-11 at 09:04 -0500, Christoph Lameter wrote:
> > Eduard - Gabriel Munteanu wrote:
> > 
> > 
> > 
> > >  static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> > >  {
> > > +	void *ret;
> > > +
> > >  	if (__builtin_constant_p(size) &&
> > >  		size <= PAGE_SIZE && !(flags & SLUB_DMA)) {
> > >  			struct kmem_cache *s = kmalloc_slab(size);
> > > @@ -239,7 +280,13 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> > >  		if (!s)
> > >  			return ZERO_SIZE_PTR;
> > >  
> > > -		return kmem_cache_alloc_node(s, flags, node);
> > > +		ret = kmem_cache_alloc_node_notrace(s, flags, node);
> > > +
> > > +		kmemtrace_mark_alloc_node(KMEMTRACE_TYPE_KMALLOC,
> > > +					  _THIS_IP_, ret,
> > > +					  size, s->size, flags, node);
> > > +
> > > +		return ret;
> > 
> > You could simplify the stuff in slub.h if you would fall back to the uninlined
> > functions in the case that kmemtrace is enabled. IMHO adding additional inline
> > code here does grow these function to a size where inlining is not useful anymore.
> 
> So, if CONFIG_KMEMTRACE is enabled, make the inlined version go away
> completely? I'm okay with that though I wonder if that means we now take
> a performance hit when CONFIG_KMEMTRACE is enabled but tracing is
> disabled at run-time...

Oh, good. I'm also thinking to add a macro that expands to simple inline when
CONFIG_KMEMTRACE is disabled and to __always_inline otherwise.

> > > +	kmemtrace_mark_alloc(KMEMTRACE_TYPE_CACHE, _RET_IP_, ret,
> > > +			     s->objsize, s->size, gfpflags);
> > > +
> > > +	return ret;
> > >  }
> > 
> > _RET_IP == __builtin_return_address(0) right? Put that into a local variable?
> > At least we need consistent usage within one function. Maybe convert
> > __builtin_return_address(0) to _RET_IP_ within slub?
> 
> I think we should just convert SLUB to use _RET_IP_ everywhere. Eduard,
> care to make a patch and send it and rebase this on top of that?

Sure. Will get back soon.

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