linux-kernel - Re: [patch 02/41] cpu alloc: The allocator

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Message-Id: <20080529223109.bbb7b0e0.akpm@linux-foundation.org>
Date:	Thu, 29 May 2008 22:31:09 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <clameter@....com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Eric Dumazet <dada1@...mosbay.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mike Travis <travis@....com>
Subject: Re: [patch 02/41] cpu alloc: The allocator

On Thu, 29 May 2008 22:10:25 -0700 (PDT) Christoph Lameter <clameter@....com> wrote:

> > > +		start++;
> > > +		first = 0;
> > > +	}
> > 
> > This is kinda bitmap_find_free_region(), only bitmap_find_free_region()
> > isn't quite strong enough.
> > 
> > Generally I think it would have been better if you had added new
> > primitives to the bitmap library (or enhanced existing ones) and used
> > them here, rather than implementing private functionality.
> 
> The scope of the patchset is already fairly large.

It would be a relatively small incremental effort ;)

> The search here is 
> different and not performance critical. Not sure if this is useful for 
> other purposes.

I think that strengthening bitmap_find_free_region() would end up
giving us a better kernel than open-coding something similar here.

> > > + */
> > > +
> > > +/* Return a pointer to the instance of a object for a particular processor */
> > > +#define CPU_PTR(__p, __cpu)	SHIFT_PERCPU_PTR((__p), per_cpu_offset(__cpu))
> > 
> > eek, a major interface function which is ALL IN CAPS!
> > 
> > can we do this in lower-case?  In a C function?
> 
> No. This is a macro and therefore uppercase (there is macro magic going on 
> that ppl need to be aware of). AFAICR you wanted it this way last year. C 
> function not possible because of the type checking.

urgh.  This is a C-convention versus kernel-convention thing.  The C
convention exists for very good reasons.  But it sure does suck.

What do others think?
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