Messages in this thread | | | Date | Tue, 16 Sep 2003 17:20:57 +0200 | From | Stephan von Krawczynski <> | Subject | Re: experiences beyond 4 GB RAM with 2.4.22 |
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On Tue, 16 Sep 2003 15:36:14 +0100 Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> On Maw, 2003-09-16 at 14:36, Stephan von Krawczynski wrote: > > Well, I do understand the bounce buffer problem, but honestly the current > > way of handling the situation seems questionable at least. If you ever > > tried such a system you notice it is a lot worse than just dumping the > > additional ram above 4GB. You can really watch your network connections go > > bogus which is just unacceptable. Is there any thinkable way to ommit the > > bounce buffers and still do something useful with the beyond-4GB ram parts? > > The 2.6 tree is somewhat better about this but at the end of the day if > your I/O subsystem can't do the job your box will not perform ideally.
Hm, "not ideally" is a real friendly word for describing the mess ;-) Isn't there a possibility to flag this part of the memory as nonDMA-able, kind of "do whatever you want with it, but don't expect any dma-driven i/o"... I know this gets a problem when swap jumps in, though. But really it is far better for the box to flag it more or less unusable compared to a DoS done by user-space "find" ... I know this is a real corner case of life. It looks more like taking a different decision than current to improve the situation and not so much a real development topic. Probably a note in kernel docs reading "DON'T DO THIS" is either sufficient...
Regards, Stephan
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