Can not increase Size of Shared Memory

问题

Could you please help me? I can not increase the size of my Sherd Memory. The code is written in C on Linux.

I need 65536 bytes, but just 49152 seem to be allowed... If I increase it, shmget fails...(in my code: shmid < 0) I tried to find out my maximum shared memory size and increased it with:

sysctl -w kernel.shmmax=2147483648

But that doesn't help, the initialization again fails.

This is my code:

 #define SHM_KEY                 9877

 #define SHM_SIZE                65536

int SHM_init (int shmid, char** shm, key_t key, long int size) {

    /* Create a new (System V) shared memory segment of the specified size */
    shmid = shmget(key, SHM_SIZE, IPC_CREAT|0777);

    /* Check if SHM creation was successful */
    if (shmid < 0) {
        /* DBG: Debug message to show which point of the program has been passed */
        DBG_PRINT("C\n");

        /* Check if creation failed because of already existing SHM */
        if (EEXIST == errno) {
            /* DBG: Debug message to show which point of the program has been passed */
            DBG_PRINT("CC\n");
            /* Delete already existing SHM with shmctl */
            shmctl(shmid, IPC_RMID, NULL);
        } else {
            /* DBG: Debug message to show which point of the program has been passed */
            DBG_PRINT("CCC\n");
        }

        /* Creation and initialization of SHM failed */
        return -1;
    }
    /* Attach the SHM data pointer to the previously created SHM segment */
    *shm = shmat(shmid, NULL, 0);

    if(*shm == (char *) -1) {
        /* Attaching failed */
        return -1;
    }
    DBG_PRINT("Shared Memory Initialization successful\n");
    /* Creation and initialization of shared memory was successful */
    return 0;
}

Thank you so much in advance...

回答1:

This topic might help. What does ipcs -l return if you increase the shmmax with sysctl -w kernel.shmmax=2147483648 ?

来源：https://stackoverflow.com/questions/34471969/can-not-increase-size-of-shared-memory

标签

shared-memory