How does shared memory work

It really just depends on what the game needs that extra vram for. If you aren't rendering to system RAM, you're probably not going to need all that video memory bandwidth. It's really all about when you plan to replace it, and how you expect video memory requirements to grow. DarkZV2Beta posted Sorry but it's true, if your framebuffer goes to Ram, that doubles to triples frame time He who stumbles around in darkness with a stick is blind. Sorry but it's true, if your framebuffer goes to Ram, that doubles to triples frame time If your framebuffer does, yes.

That's not all VRAM is for though. That's why Infinity Cache is a big deal; your primary framebuffers will fit into that MB. Actually, that's more like a RGBA render target. If your framebuffer does, yes.

Yep that's correct. That's why back in the late 90s a 4mb video card could run games at x Nearly all the game ran from RAM, and quite a bit of it from swap back in the day.

User Info: cleat Won't crash, will hitch n stutter so it's not a good experience. Unrelated processes say one process running in one terminal and another process in another terminal communication can be performed using Named Pipes or through popular IPC techniques of Shared Memory and Message Queues.

The above system call creates or allocates a System V shared memory segment. The first argument, key, recognizes the shared memory segment. The key can be either an arbitrary value or one that can be derived from the library function ftok. If the client wants to use shared memory with this key, then it must be a child process of the server. Also, the child process needs to be created after the parent has obtained a shared memory.

Need to pass the permissions as well. This call would return a valid shared memory identifier used for further calls of shared memory on success and -1 in case of failure. To know the cause of failure, check with errno variable or perror function.

The above system call performs shared memory operation for System V shared memory segment i. So a process has to request access to it — that's the role of shmat. By doing that, kernel will map the shared memory into process' virtual memory space.

This way, the process can read and write it. Because it's the same memory, all processes who have "attached" to it see the same contents. Any change a process makes is visible to other processes as well. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How does shared memory work behind the scene in Linux?

Ask Question. Asked 4 years ago. Active 2 years, 11 months ago. The only performance issue with shared memory is bank conflicts, which we will discuss later. Note that on devices of Compute Capability 1. The other three kernels in this example use dynamically allocated shared memory, which can be used when the amount of shared memory is not known at compile time.

In this case the shared memory allocation size per thread block must be specified in bytes using an optional third execution configuration parameter, as in the following excerpt. The dynamic shared memory kernel, dynamicReverse , declares the shared memory array using an unsized extern array syntax, extern shared int s[] note the empty brackets and use of the extern specifier.

The size is implicitly determined from the third execution configuration parameter when the kernel is launched. The remainder of the kernel code is identical to the staticReverse kernel. What if you need multiple dynamically sized arrays in a single kernel? You must declare a single extern unsized array as before, and use pointers into it to divide it into multiple arrays, as in the following excerpt. To achieve high memory bandwidth for concurrent accesses, shared memory is divided into equally sized memory modules banks that can be accessed simultaneously.

Therefore, any memory load or store of n addresses that spans b distinct memory banks can be serviced simultaneously, yielding an effective bandwidth that is b times as high as the bandwidth of a single bank. The hardware splits a conflicting memory request into as many separate conflict-free requests as necessary, decreasing the effective bandwidth by a factor equal to the number of colliding memory requests.

An exception is the case where all threads in a warp address the same shared memory address, resulting in a broadcast. Devices of compute capability 2. To minimize bank conflicts, it is important to understand how memory addresses map to memory banks. Shared memory banks are organized such that successive bit words are assigned to successive banks and the bandwidth is 32 bits per bank per clock cycle.