chuck gelm wrote:
Pratik Solanki wrote:
[CCing linux-newbie]
On Thu, 7 Oct 2004 18:21:57 +0100 (BST), Ankit Jain
<[EMAIL PROTECTED]> wrote:
well i dont know exactly but somewhat i feel that
there must be some way to disable the virtual memory.
yaa of course there should be some way. it is not that
sys cant work without it
Yes, you can have a system without virtual memory. Search for MMUless linux kernel and you'll see patches/websites.
My point was that disabling VM after its been enabled would tough (if not impossible). Someone correct me if I am wrong here.
Pratik.
I was thinking that an active swap partition was 'virtual memory'. Why are many folks using capital letters 'VM'. Am I missing something? Is 'VM' == virtual memory or is there a application or service called 'VM' ?
Anywho, the only 'virtual memory' I know of is an active swap file or swap partition and either can be started or stopped in a running kernel. (I think.)
Regards, Chuck
From "Understanding the Linux Kernel":
"Virtual memory acts as a logical layer between the application memory requests and the hardware Memory Management Unit (MMU)."
It is an abstraction of system memory to provide an architecture-independent memory interface. It allows for a great many things, including swap functionality, but its primary function is to make the details of memory management invisible to application programmers. You just malloc() some memory, and you don't have to worry overmuch about far jumps, hardware cache alignment, or other annoying stuff.
It also allows large malloc() calls to succeed, even if physical memory is completely fragmented, by maintaining a set of page tables that allow virtual-to-physical mapping of memory addresses.
This is one of the most challenging areas of kernel development, and very hardware-specific. I tried to understand how it worked recently, gave myself a splitting headache after 30 minutes, and decided to let it sit for another year or so until I understand kernel internals, computer architecture, and assembler much better than I do now :)
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