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Date:      Sat, 12 Oct 2002 13:52:45 +0100
From:      Christoph Hellwig <hch@infradead.org>
To:        Wes Peters <wes@softweyr.com>
Cc:        Matthew Dillon <dillon@apollo.backplane.com>, "Vladimir B. Grebenschikov" <vova@sw.ru>, Nate Lawson <nate@root.org>, arch@FreeBSD.ORG
Subject:   Re: Database indexes and ram (was Re: using mem above 4Gb was:swapon some regular file)
Message-ID:  <20021012135245.A16453@infradead.org>
In-Reply-To: <3DA4C271.37AACAA3@softweyr.com>; from wes@softweyr.com on Wed, Oct 09, 2002 at 04:57:37PM -0700
References:  <Pine.BSF.4.21.0210081209010.11243-100000@root.org> <1034105993.913.1.camel@vbook.express.ru> <200210082015.g98KFFrq084625@apollo.backplane.com> <1034109053.913.7.camel@vbook.express.ru> <200210082051.g98KpjU1084793@apollo.backplane.com> <3DA4C271.37AACAA3@softweyr.com>

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On Wed, Oct 09, 2002 at 04:57:37PM -0700, Wes Peters wrote:
> Linux solved this problem by refusing to do it.  The candidates for DMA
> transfers include skbufs and buffers from the disk buffer pool, both of
> which are allocated from the lowest 4GB of physical ram when using PAE
> mode.

Umm, Linux _does_ DMA into any memory if the NIC/HBA/whatever supports
it.


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