Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?] | Date | Mon, 6 May 2002 17:26:19 +0200 |
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On Monday 06 May 2002 10:54, Roman Zippel wrote: > Hi, > > On Mon, 6 May 2002, Daniel Phillips wrote: > > > I must be guilty of not explaining clearly. Suppose you have the following > > physical memory map: > > > > 0: 128 MB > > 8000,0000: 128 MB > > 1,0000,0000: 128 MB > > 1,8000,0000: 128 MB > > 2,0000,0000: 128 MB > > 2,8000,0000: 128 MB > > 3,0000,0000: 128 MB > > 3,8000,0000: 128 MB > > > > The total is 1 GB of installed ram. Yet the kernel's 1G virtual space, > > can only handle 128 MB of it. The rest falls out of the addressable range and > > has to be handled as highmem, that is if you preserve the linear relationship > > between kernel virtual memory and physical memory, as config_discontigmem does. > > Even if you go to 2G of kernel memory (restricting user space to 2G of virtual) > > you can only handle 256 MB. > > Why do you want to preserve the linear relationship between virtual and > physical memory?
I don't, I observed that in all known instances of config_discontigmem, that linear relationship is preserved. Now, you and Andrea are suggesting that no such linear relation is strictly necessary and I believe its worth investigating further, to see how it would work and how it compares to config_nonlinear.
> There is little common code (and only during > initialization), which assumes a direct mapping. I can send you the > patches to fix this.
I already have patches to do that, that is, config_nonlinear. I'm interested in looking at your patches though, because we might as well give all the different approaches a fair examination.
> Then you can map as much physical memory as you want > into a single virtual area and you only need a single pgdat.
You're talking about your 68K solution with the loops that search through memory regions? If so, I've already looked at it and understand it. Or, if it's a new approach, then naturally I'd be interested.
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