linux-kernel - Re: Memory allocation from ZONE

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Message-ID: <alpine.DEB.2.00.1107141432520.2923@router.home>
Date:	Thu, 14 Jul 2011 14:34:04 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Pintu Agarwal <pintu_agarwal@...oo.com>
cc:	Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Memory allocation from ZONE_HIGHMEM ???

On Wed, 13 Jul 2011, Pintu Agarwal wrote:

> I have a question regarding kernel memory allocation(using kmalloc) from ZONE_HIGHMEM zone.

kmalloc does not allocate from ZONE_HIGHMEM.

> But I want to specifically allocate pages from ZONE_HIGHMEM instead of Normal zone.
> How to explicitly do that in kernel?

You must use the page allocator. The slab allocators cannot use
ZONE_HIGHMEM. ZONE_HIGHMEM contains pages that are not directly accessible
from the processor.