Messages in this thread | | | Subject | Re: Linux and physical memory | From | Corey Minyard <> | Date | 18 Jan 1999 22:19:23 -0600 |
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Max <max@Linuz.sns.it> writes: > > Even if english is not my native language, I thought my question was clear: > > >> I don't understand why the kernel needs to always have all physical memory > >> mapped in its address space. > > I said "ALWAYS have mapped ALL physical memory" etc. > > So I obviously mean (well, lokkgin to your answer maybe it was not so obvious): > > Why can't the kernel just map in its address space the pieces of RAM it needs > for kernel code/data, and unmap them when done with them? > User code/data would always be accessible (I am not suggesting to touch user > processes address space) so I thought that could work and remove the 960MB > problem. > > Maybe that mapping/unmapping of memory in kernel address space is expensive, > but I don't know. So I posted the question. > > Massimiliano Ghilardi
From my understanding of the buffer cache, a buffer can be anywhere in memory (excluding kernel code and data areas).
And yes, mapping and unmapping is rather expensive because it involves messing with page tables.
-- Corey Minyard Internet: minyard@acm.org Work: minyard@nortel.ca UUCP: minyard@wf-rch.cirr.com
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