Date: Sun, 13 Oct 2002 06:06:48 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: ticso@cicely.de, ticso@cicely8.cicely.de Cc: hch@infradead.org, wes@softweyr.com, dillon@apollo.backplane.com, vova@sw.ru, nate@root.org, arch@FreeBSD.org Subject: Re: Database indexes and ram Message-ID: <20021013.060648.93373269.imp@bsdimp.com> In-Reply-To: <20021013103538.GG17920@cicely8.cicely.de> References: <20021012135245.A16453@infradead.org> <20021012.150616.129769790.imp@bsdimp.com> <20021013103538.GG17920@cicely8.cicely.de>
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In message: <20021013103538.GG17920@cicely8.cicely.de>
Bernd Walter <ticso@cicely8.cicely.de> writes:
: On Sat, Oct 12, 2002 at 03:06:16PM -0600, M. Warner Losh wrote:
: > In message: <20021012135245.A16453@infradead.org>
: > Christoph Hellwig <hch@infradead.org> writes:
: > : 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.
: >
: > Unless the card is 64bit, it can't DMA past 4G.
:
: Shouldn't all modern pci chips support two 32bit word addresses.
I don't think so. There's only 32-bits on the bus for the address on
most pci cards (not the 64-bit pci cards, which are special), so I
don't see how they can go above 4G. Unless I'm being unusually dense
this morning.
Warner
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