Questions tagged [shared-memory]
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80 questions
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What is the contribution of API to the memory usage of a process in linux as shown by pmap command?
I am trying to understand the memory usage of my program excluding the contribution of custom made API that creates and attaches to shared memory segment. Following is the API code. I have included ...
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185views
Which consistency guarantees do POSIX shared memory objects have?
On Linux, POSIX shared memory objects [1] use a tmpfs via /dev/shm. A tmpfs in turn is said to "live completely in the page cache" [2] (I'm assuming swap has not been enabled). I am ...
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Can mmap be used to create a file which references memory subset of another file?
I'm interested in writing a program that can create two files, second file would be a "view" of first file and if modified, the first file would also be modified. Is this possible to do with ...
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763views
Why does ftruncate with a shared memory object not use memory?
I've observed that I can create a shared memory object and give it ostensibly any size with ftruncate, regardless of the resource limits on my system. The code below sets the size to 262 TB, and ...
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Is it possible for two processes to use the same shared-memory without resorting to a file to obtain it, be it a memory-mapped file or /dev/shm file?
I'm curious because today the only way I know how to give two different processes the same shared-memory is through a memory-mapped file, in other words, both processes open the same memory-mapped ...
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1answer
5kviews
How to Add some System Memory to be shared with the GPU in Linux?
I have switched from Windows 10 to linux mint 21.1 I tried playing GTA 5 on lutris (wine emulation) however the game is almost unplayable on linux as big parts of the map will not load because of my ...
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1answer
287views
Using IPC_CREAT with an already created shared memory segment
I am trying to figure out what will happen if I use the IPC_CREAT flag with shmget(). I have used a key of an already created shared memory segment from another process. When I did so, the calling ...
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1answer
275views
Shared Memory using shmget() and shmat()
We can create and attach a shared memory to a process using shmget() and shmat(). What will happen if we don't destroy and detach the shared memory in Ubuntu OS ? According to my understanding it will ...
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shmget() and shmat()
Using shmget(), we can allocate a shared memory block of certain size in bytes and using shmat(), we attach this shared memory block to the address space of the calling process. I need to check my ...
1vote
1answer
136views
What shared memory is not controlled by SHMAX/SHMALL?
We are debugging a situation where the cached/shared memory increase and increase until the system reach OOM-killer. We have set shmax and shmall in sysctl.conf but without any visible effect. Do we ...
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Issues Using GPSD as Source for Chronyd
I am attempting to use a USB GPS without PPS dongle as the sole time source on Ubuntu 18.04. GPSD appears to be working correctly since cgps reports a 3D fix. However, I can't get chrony to see the ...
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How pass a queue of data from kernel to user space?
I'm currently writing a module for Linux, and I want to pass a queue of data from kernel to user space (my program in userland being responsible for read this data - and then responsible for writing ...
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1answer
750views
Browser (Opera, Chromium...) start causing Permission denied (13) error for shared memory
Using Manjaro / Arch linux, I wanted to install another browser. However, no matter whether I installed Opera or Chromium (via pacman) I always get an error when executing it (from both Application ...
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72views
Can a process share unused memory with others?
I want to run about 200 processes with my experiments. Every of them really needs less than a GB: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24688 rinkman 20 0 ...
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922views
Shared memory using shmget()
According to my understanding about shared memory is that it is a memory segment that is shared between two or more processes. Shared memory can be implemented using shmget() . However , since any ...
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