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Do threads have their own virtual memory?
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.
Is virtual memory real memory?
In a virtual memory system, disk or other storage is used to extend the size of RAM, also known as real memory or physical memory. Since disk is much cheaper than RAM, this offers an inexpensive way to increase the memory available to programs. The disk space used for this purpose is known as swap space.
Is virtual memory really useful?
Virtual memory, also known as the swap file, uses part of your hard drive to effectively expand your RAM, allowing you to run more programs than it could otherwise handle. But a hard drive is much slower than RAM, so it can really hurt performance. RAM is faster than storage, and you have much less of it.
What is the difference between real memory and virtual memory?
Real mem relates to physical memory (actual RAM modules in your computer). Virtual Mem is how much “fake” memory is allocated to the process, meaning memory that is allocated on the permanent storage medium (hard drive, solid state drive, etc) for that process.
Can virtual memory be bigger than physical memory?
Virtual memory is usually much larger than physical memory, making it possible to run programs for which the total code plus data size is greater than the amount of RAM available. This paging is performed automatically by collaboration between the CPU, the memory management unit (MMU), and the operating system kernel.
What happens if virtual memory is too high?
The bigger the virtual memory space, the bigger the adress table becomes in which is written, which virtual adress belongs to which physical adress. A big table can theoreticaly result in slower translation of the adresses and therefore in slower reading and writing speeds.
What kind of memory does a thread use?
If thread uses heap (not only stack), then it needs more memory, and in that case you can start less threads. The simple answer to your question is, they use virtual memory. everything uses virtual memory except a handful of processes related to the OS.
How do threads of a process work in the same virtual memory?
In the abstract, that means that one thread’s stack runs from A to B, and a different thread’s stack runs from C to D, where A < B < C < D (i.e., the A-B range doesn’t overlap with the C-D range). Is the stack the only part in virtual memory that is unique per thread in Linux? The uniqueness of the stacks isn’t related to virtual memory.
How many threads do you need for multithreading?
How many threads you can start depends on the memory size and how much memory is needed per thread. If thread uses heap (not only stack), then it needs more memory, and in that case you can start less threads.
When to use virtual memory or real memory?
And as James explain in his answer decision on Ram vs HDD is taken by Kernel using algorithims such as LRU. It’s up to the kernel to make sure the virtual memory you want is cached into RAM when you want it – unless you’re writing your own userspace VM layer (such as databases often do, iiuc), just don’t worry about it.