linux-kernel - Re: memset as memzero

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Message-ID: <alpine.LFD.0.999.0709221149480.16478@woody.linux-foundation.org>
Date:	Sat, 22 Sep 2007 11:53:53 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Arjan van de Ven <arjan@...radead.org>
cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: memset as memzero

On Sat, 22 Sep 2007, Arjan van de Ven wrote:
> 
> it doesn't add value.... memset with a constant 0 is just as fast
> (since the compiler knows it's 0) than any wrapper around it, and the
> syntax around it is otherwise the same.

Indeed.

The reason we have "clear_page()" is not because the value we're writing 
is constant - that doesn't really help/change anything at all. We could 
have had a "fill_page()" that sets the value to any random byte, it's just 
that zero is the only value that we really care about.

So the reason we have "clear_page()" is because the *size* and *alignment* 
is constant and known at compile time, and unlike the value you write, 
that actually matters.

So "memzero()" would never really make sense as anything but a syntactic 
wrapper around "memset(x,0,size)". 

			Linus
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