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Date: Tue, 8 Apr 2008 10:04:46 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>, "H. Peter Anvin" <hpa@zytor.com>,
       LKML <linux-kernel@vger.kernel.org>, Yinghai Lu <yhlu.kernel@gmail.com>
Subject: Re: bootmem allocator
Message-ID: <20080408080446.GA12308@elte.hu>
References: <20080407185613.GD9211@cvg> <20080407190904.GH12292@elte.hu> <87iqytqwl7.fsf@basil.nowhere.org>
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* Andi Kleen <andi@firstfloor.org> wrote:

> > hm, bootmem allocator is supposed to clear memory. We have a couple 
> > of places that rely on that.
> 
> I was actually considering to change that for the GB pages hugetlbfs 
> patchkit, because memset for 1G is a little slow and not needed (will 
> be cleared later anyways) and it might be a problem for very large 
> systems with a lot of such pages at boot.

changing the default behavior of bootmem alloc to be non-clearing is a 
really bad idea that will only cause unrobustness. The proper approach 
is to add an _opt-in_ API that does not clear memory 
(bootmem_alloc_dontclear() or whatever), available to callers that know 
it for sure that they dont need the clearing.

	Ingo