how much memory is my kernel module using?

Question

lsmod , /proc/modules and slabinfo , /proc/meminfo does NOT give how much memory my kernel module is using

is there a way to find this out ?

btw, I wrote a small test program basically, a device driver that takes ioctl call to alloc 1MB and I send this ioctl message every second from my application so my drive does kmalloc every second. Iam not able to see the increase in "cat /proc/meminfo | grep Slab "

-- snip ---

int device_ioctl(
         struct file *file,
         unsigned int ioctl_num, 
         unsigned long ioctl_param)
{
    /* 
     * Switch according to the ioctl called 
     */
    printk ( "<l> inside ioctl %d IOCTL_ALLOC_MSG = %d\n", ioctl_num,IOCTL_ALLOC_MSG );
    switch (ioctl_num) {
    case IOCTL_ALLOC_MSG:
        allocfunc(); // kmalloc 1MB // printk in this function is OK
        break;
    case IOCTL_DEALLOC_MSG:
        deallocfunc();
        break;
    }

    return 0;
}

---

Application/user space

 while ( !stop )
        {
            ret_val = ioctl(memfile, IOCTL_ALLOC_MSG);

            if (ret_val < 0) {
                printf("ioctl failed. Return code: %d, meaning: %s\n", ret_val, strerror(errno));
                return -1;
            }
            sleep ( 10 );

        }

I dont see the growth of memory in slabinfo. I know linux does cache->slabs->pages->objects but there must be some way in user land to determine the memory size of a particular kernel module.

Thanks,

Answer 1

I'm not sure if it will be ok for you, but you can get the amount of memory that a module has taken with 'cat /proc/modules' , the second column is the size in bytes that the module in the first column is using.

Sample output showing how much memory are drm modules using:

cat /proc/modules |grep ^drm|awk '{print $1 " " $2}'

drm_kms_helper 49394 drm 286028

Hope that helps.

Answer 2

Assuming there isn't a way to do this directly (which there might be, for all I know) ....

You could use LTTng to trace your kernel events. If there's no handy event already there, you should create a new trace even every time your module allocates memory.

You can then analyse the trace and draw a graph of how your memory use grows and shrinks over time.