quartz/content/notes/18-processes-sharing-and-threads.md

title	aliases	tags
18-processes-sharing-and-threads		cosc204 lecture

Shared memory for processes

Can't assume all variables are initally zero. OS decide which process maps who which physical address

memory mapping mmap is a family of system calls:

• allow two processes to share some region of their memory space.
• achieved by creating a memory region that can be shared by other processes

shared memory by two processes mapping to the same file or using fork() after mmap()

random_fd = open("/home/hzy/test/zero", O_RDWR);
ptr = mmap(NULL, 10240, PROT_READ|PROT_WRITE,
	MAP_SHARED | MAP_FILE, random_fd, 0);

private mapping is often ysed to set up new memory sections.

fd = open("mmap_test_file", O_RDWR); p
tr = mmap(NULL, 10240, PROT_READ|PROT_WRITE, 
	MAP_PRIVATE|MAP_FILE, fd, 0);

Threads

Lightweight process - shares everything except the stack