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Old 12-17-2006, 10:21 AM   #1
cs_raja
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Registered: Sep 2004
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Unhappy Memory management ??????


My doubt is regarding 32 bit systems.

And Kernel will take around 1 GB of memory and this is common to all processes. Each process will map this to their starting wirtual addresses.

My doubt is, Is this 4 GB limit is for one process or all the processes together in the system.

As far as I know wiht Virtual Memory management one can address maximum of 4 GB(32 bit). It ok if all processes can address 4 GB combined.
Is it that each process is allocated a separate address inside a single 4 GB adress space

OR

If each process can address 4 Gb then how is it managed.
Does any body have any clue

Thankx
 
Old 12-17-2006, 11:18 AM   #2
btmiller
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Each process has a 4 GB virtual memory space. As you say, the top 1 GB (usually) of the address space is reserved for the kernel and common to all processes, but the other 3 GB is exclusive to the process (excluding consideration like shared memory here). The total amount of memory used by all processes may exceed 4 GB, but this would require the use of swap space as a 32 bit kernel can only access 4 GB of physical memory (remember that the user and kernel memory that I talk about above refer to virtual addresses, which are translated to physical addresses via the MMU on the CPU using rules given by the kernel). Therefore, all the processes in the system may use more memory than the physical memory installed, but no more than physical memory plus swap space (or any other backing store).
 
  


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