On Tue, 15 Sep 1998, Helge Hafting wrote: > In <[EMAIL PROTECTED]>, on 09/14/98 > at 04:56 PM, " Raymond A. Ingles" <[EMAIL PROTECTED]> said: [...] > > Unfortunately, the PC ISA DMA controller can't address memory beyond the > >first 16MB. So, when a DMA buffer is requested, the kernel has to find a > >continuous chunk of memory that is physically below 16MB. If it can't > >find it, too bad. > > The kernel should then swap something below 16M out, or preferably push it > above 16M. Anybody know why it doesn't do that? I find it unlikely that > *all* memory below 16M should be locked for i/o or something.
I don't know all the details about why the kernel can't do that, but I'm given to understand that performance would suffer, and some programs would break. There was a discussion on linux-kernel a while ago, maybe it's archived somewhere. Sincerely, Ray Ingles (248)377-7735 [EMAIL PROTECTED] Modern inductive method: 1) Devise hypothesis. 2) Apply for grant. 3) Perform experiments. 4) Revise data to fit hypothesis. 5) Publish.
