Messages in this thread | | | Date | Thu, 17 Mar 2005 14:08:13 -0500 (EST) | From | linux-os <> | Subject | Re: Kernel memory limits? |
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On Thu, 17 Mar 2005, Peter W. Morreale wrote:
> (I did not see this addressed in the FAQs...) > > How much physical memory can the 2.4.26 kernel address in kernel context on > x86? >
All of it.
> What about DMA memory? >
All of it, too. The old DMA controller(s) could only address 16 MB because that's all the page-registers allowed. Bus-mastering DMA off the PCI/Bus has no such limitation. Most have DMA controllers that use scatter-lists so RAM doesn't even have to be contiguous, only properly allocated (in pages) and nailed down with no caching.
> Local rumor says ~1GB. But this makes little sense given a 32-bit address. >
If you are looking for a dynamic buffer in DMA-able RAM, you probably can only use aout 1GB, but that's not how to do DMA.
> Where in the source can I learn more about this? >
../linux-`uname -r`/mm
> Thanks, > -PWM
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