Yes, it’s definitely possible for the same address to map to different physical memory depending on the process that’s referencing it.
Table of Contents
What happens if you map multiple virtual memory pages to same physical memory address?
Multiple programs or processes can share the main memory without reading or writing into each other’s address space. This is enforced by virtual memory. Virtual memory also allows for sharing of data or code between programs by having two virtual addresses point to the same physical memory location.
Can 2 processes use the same page?
The answer is YES. @Syed. Waris Usually the kernel code and data is present in all address spaces/processes.
Can references to two different virtual addresses map to the same physical address?
This is because both 0 to 4 MB and 2 GB to (2 GB + 4 MB) in the virtual address space are mapped to the same memory location (0 to 4 MB) in the physical address space. Hence, it is possible for two virtual addresses VA1 and VA2 to point to the same physical address PA.
Can two running processes share the complete process image in physical memory?
(b) Can two running processes share the complete process image in physical memory (not just parts of it)? Ans: (a) Yes, two processes can run the same program.
Can processes share address space?
Each process has a separate memory address space, which means that a process runs independently and is isolated from other processes. It cannot directly access shared data in other processes.
Can two threads corresponding to two different processes write to the same physical memory address?
Yes. Each thread has its own stack, but all the memory associated with the process is in the same virtual address space. If a function in one thread had a pointer to a stack-allocated variable in another thread, that function could read from/write to that variable.
How does multi level paging work?
Multilevel Paging is a paging scheme that consists of two or more levels of page tables in a hierarchical manner. It is also known as hierarchical paging. The entries of the level 1 page table are pointers to a level 2 page table and entries of the level 2 page tables are pointers to a level 3 page table and so on.
How do I convert virtual memory to physical memory?
Do processes share page tables?
Yes every process has its own pagetables. They might be shared with the parent process(copy on write) or with other processes(shared memory).
Can a process have more than one page table?
Since each process has a different page table, there is not one pmap that will work for every process. Every process will have its own pmap function, which will allow each process to use a different page table and possibly even page tables of different formats.
Why is kernel mapped to the same address space as processes?
The reason why kernel is mapped into userspace is mostly performance-related. Kernel can also set own different page table at any time to access physical memory it wants, but that would also trash all caches and degrade performance dramatically.
How do you map a physical address to a virtual address?
MMU(Memory Management Unit) : The run time mapping between Virtual address and Physical Address is done by a hardware device known as MMU. In memory management, the Operating System will handle the processes and move the processes between disk and memory for execution . It keeps track of available and used memory.
What is the difference between physical address and virtual address?
The logical address does not exist physically in the memory, and therefore it is sometimes known as a virtual address. The physical address is a location in the memory unit. The logical address is used as a reference to access the physical address. The physical address cannot be accessed directly.
What is difference between physical address and logical address?
Physical Address is the actual address of the data inside the memory. The logical address is a virtual address and the program needs physical memory for its execution. The user never deals with the Physical Address.
Is it possible for a process to have two working sets one representing data and another representing code explain?
Yes, in fact many processors provide two TLBs for this very reason. As an example, the code being accessed by a process may retain the same working set for a long period of time. However, the data the code accesses may change, thus reflecting a change in the working set for data accesses.
Do child and parent processes share memory?
Answer: Only the shared memory segments are shared between the parent process and the newly forked child process. Copies of the stack and the heap are made for the newly created process.
Does a forked process share memory?
What fork() does is the following: It creates a new process which is a copy of the calling process. That means that it copies the caller’s memory (code, globals, heap and stack), registers, and open files.
Do threads share same memory?
In a multi-threaded process, all of the process’ threads share the same memory and open files. Within the shared memory, each thread gets its own stack. Each thread has its own instruction pointer and registers.
Are threads faster than processes?
On a multiprocessor system, multiple threads can concurrently run on multiple CPUs. Therefore, multithreaded programs can run much faster than on a uniprocessor system. They can also be faster than a program using multiple processes, because threads require fewer resources and generate less overhead.
Why do we need two-level paging?
This is Two-level Paging because here we got 2 page tables. But If still the size of page table is more than the Frame Size then we have to continue till we reach a stage where the size of Outer Most Table is less than the Frame Size. This Concept is called as MultiLevel Paging.
Why are multi level page tables better?
The advantage of a multilevel (hierarchical) page table over a single-level one is: (a) Page number lookups are faster. (b) The page table can consume much less space if there are large regions of unused memory. (c) Each segment (code, data, stack) can be managed separately.
What is segmented paging?
In Segmented Paging, the main memory is divided into variable size segments which are further divided into fixed size pages. Pages are smaller than segments. Each Segment has a page table which means every program has multiple page tables.
How do I get a physical address from a page table?
- look up the page number in the page table and obtain the frame number.
- to create the physical address, frame = 17 bits; offset = 12 bits; then 512 = 29. 1m = 220 => 0 – ( 229-1 ) if main memory is 512 k, then the physical address is 29 bits.
How virtual address is translated to physical address?
The CPU manages translation of virtual to physical addresses using its Memory Management Unit (MMU). A virtual address is specified as a offset from the start of a memory segment; these segments are used by the kernel and user processes to hold their text, stack, data, and other regions.