What is the shared memory of big data's interprocess communication?

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Shared memory:

Data transfer between processes is the most efficient in the system v version, but it is not synchronized and mutually exclusive, so it is often used in conjunction with semaphores.

Nattch: indicates how many processes are attached to shared memory. To see its value, use the ipcs-m command

Delete key value with ipcrm-m + key value

Graphics understand shared memory:

# include

# include

1. Create a shared memory function:

Int shget (key_t key,size_t size, int shmflg* buf)

The second parameter is its size, which is generally 4k, or an integer multiple of 4096.

The third parameter is generally: IPC_CREAT | IPC_EXCL

two。 Function that destroys shared memory:

Int shmctl (int shm _ id,int cmd,int shmflg* buf)

The second parameter is generally: IPC_RMID

3. Hang on to shared memory:

Void * shmat (int shmid, const void * shmaddr, int shmflg)

4. Disassociate shared memory

Int shmdt (const void * shmaddr)

Shared memory implementation code:

/ / comm.h 1 # include 2 # include 3 # include 4 # include 5 # include 6 # define _ PATH_. "7 # define _ PROJ_ID_ 0X7777 8 # define _ SIZE_ 4096 9 int shm_create () 10 {11 key_t key=ftok (_ PATH_, _ PROJ_ID_); 12 if (key)