It is an arbitrary question that popped in my mind. However, I came to know that the constraints I stated in the previous mail is only restricted to x86 only.Now besides my first questions , I have one more question, Why x86 only?
On Tue, May 14, 2013 at 2:34 AM, Sergio Andrés Gómez del Real < sergio.g.delr...@gmail.com> wrote: > Sure, I forgot what you said; precisely the mechanism allows to use > lots of linear space without necessarily allocating physical memory > (demand paging and the like). > What about the rest of what I said? Is it correct or is there > something wrong about it? > Thanks. > > On 5/13/13, valdis.kletni...@vt.edu <valdis.kletni...@vt.edu> wrote: > > On Mon, 13 May 2013 14:11:22 -0500, Sergio Andr said: > > > >> 2. When user applications allocates memory, the kernel must allocate > >> virtual memory and physical memory, right? > > > > Wrong. If userspace allocates (say) 15M of memory, the kernel has every > > right > > to overcommit and not actually allocate either physical memory or backing > > page > > space for all 15M. It instead maps it as a non-existent virtual address, > > and > > if/when the application actually touches the page, it generates a page > > fault, > > and *then* the kernel does the allocating of physical memory and maybe > swap > > space. > > > > > -- *Regards,* *Paul Davies C* vivafoss.blogspot.com
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