linux-kernel - Re: [PATCH v7 01/16] hashtable: introduce a small and naive hashtable

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Message-ID: <20121029162221.GB19346@Krystal>
Date:	Mon, 29 Oct 2012 12:22:21 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Sasha Levin <levinsasha928@...il.com>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
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Subject: Re: [PATCH v7 01/16] hashtable: introduce a small and naive
	hashtable

* Tejun Heo (tj@...nel.org) wrote:
> Hello,
> 
> On Mon, Oct 29, 2012 at 12:14:12PM -0400, Mathieu Desnoyers wrote:
> > Most of the calls to this initialization function apply it on zeroed
> > memory (static/kzalloc'd...), which makes it useless. I'd actually be in
> > favor of removing those redundant calls (as I pointed out in another
> > email), and document that zeroed memory don't need to be explicitly
> > initialized.
> > 
> > Those sites that need to really reinitialize memory, or initialize it
> > (if located on the stack or in non-zeroed dynamically allocated memory)
> > could use a memset to 0, which will likely be faster than setting to
> > NULL on many architectures.
> 
> I don't think it's a good idea to optimize out the basic encapsulation
> there.  We're talking about re-zeroing some static memory areas which
> are pretty small.  It's just not worth optimizing out at the cost of
> proper initializtion.  e.g. We might add debug fields to list_head
> later.

Future-proofness for debugging fields is indeed a very compelling
argument. Fair enough!

We might want to document this intent at the top of the initialization
function though, just in case anyone want to short-circuit it.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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