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Date: Mon, 08 Aug 2005 12:11:21 +0200
Message-ID: <s5hacjs68mu.wl%tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Adrian Bunk <bunk@stusta.de>
Cc: Pekka J Enberg <penberg@cs.Helsinki.FI>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org, pmarques@grupopie.com
Subject: Re: [PATCH] kernel: use kcalloc instead kmalloc/memset
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At Sat, 6 Aug 2005 17:09:40 +0200,
Adrian Bunk wrote:
> 
> On Fri, Aug 05, 2005 at 09:52:32AM +0300, Pekka J Enberg wrote:
> >...
> > --- 2.6.orig/mm/slab.c
> > +++ 2.6/mm/slab.c
> > @@ -2555,6 +2555,20 @@ void kmem_cache_free(kmem_cache_t *cache
> >  EXPORT_SYMBOL(kmem_cache_free);
> >  
> >  /**
> > + * kzalloc - allocate memory. The memory is set to zero.
> > + * @size: how many bytes of memory are required.
> > + * @flags: the type of memory to allocate.
> > + */
> > +void *kzalloc(size_t size, unsigned int __nocast flags)
> > +{
> > +	void *ret = kmalloc(size, flags);
> > +	if (ret)
> > +		memset(ret, 0, size);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(kzalloc);
> > +
> > +/**
> >   * kcalloc - allocate memory for an array. The memory is set to zero.
> >   * @n: number of elements.
> >   * @size: element size.
> > @@ -2567,10 +2581,7 @@ void *kcalloc(size_t n, size_t size, uns
> >  	if (n != 0 && size > INT_MAX / n)
> >  		return ret;
> >  
> > -	ret = kmalloc(n * size, flags);
> > -	if (ret)
> > -		memset(ret, 0, n * size);
> > -	return ret;
> > +	return kzalloc(n * size, flags);
> >  }
> >  EXPORT_SYMBOL(kcalloc);
> 
> 
> Looking at how few is left from kcalloc, can't we make it a
> "static inline" function in slab.h?
> 
> This would optimize nicely for all of the users where the first or even 
> the first two parameters are constant at compile-time and shouldn't do 
> much harm for the other users.
> 
> As a side effect, the difference between kcalloc(1, ...) and kzalloc() 
> would become a coding style question without any effect on the generated 
> code.

How about to use __builtin_constant_p() like kmalloc?
The code readability would be worsen, though...


Takashi