From: Andi Kleen <ak@suse.de>
To: "Dave Airlie" <airlied@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
"Linus Torvalds" <torvalds@osdl.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: GFP_DMA32 and PAE x86 machines
Date: Thu, 31 May 2007 00:24:25 +0200 [thread overview]
Message-ID: <200705310024.25937.ak@suse.de> (raw)
In-Reply-To: <21d7e9970705301507o2a89e824xdc6a980e8dbedaaf@mail.gmail.com>
On Thursday 31 May 2007 00:07:45 Dave Airlie wrote:
> Depending on split all lowmem is below 1GB which isn't exactly
> optimal, I'd llike all 4GB for DMA.
Well it would be for a quite specialized limited use case:
- Memory the kernel doesn't need to map (after all kmap is evil)
- You need more than 500MB or so.
- 32bit kernel and user cannot run 64bit kernel
- Machine has >3GB of RAM
Is there clear evidence that is a common issue? If it is just a "would
be nice to have in theory" the cost of doing a GFP_DMA32 for i386 would be
probably not worth doing it. If it's a common issue it might be
considered, although the "here's a nickle. buy yourself a 64bit CPU"
strategy would also sound attractive.
Please give a very very strong rationale why you want it. Did you actually
run into such a situation yourself yet?
-Andi
next prev parent reply other threads:[~2007-05-30 22:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-30 21:10 GFP_DMA32 and PAE x86 machines Dave Airlie
2007-05-30 21:29 ` H. Peter Anvin
2007-05-30 22:07 ` Dave Airlie
2007-05-30 22:13 ` H. Peter Anvin
2007-05-30 22:24 ` Andi Kleen [this message]
2007-05-30 22:31 ` H. Peter Anvin
2007-05-30 23:09 ` Dave Airlie
2007-05-30 23:21 ` William Lee Irwin III
2007-05-31 12:11 ` Andi Kleen
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