Allocating 16MB of kernel space _get_free_pages

Hello,

I tried to call _get_free_pages (GFP_KERNEL,12) in order to allocate 16MB of continuous kernel memory.

I do it only once when the user tries to open the device.

The call returns 0. So the allocation fails.

How can I allocate 16MB in the kernel ?

According to chapter 8 in the Device Driver book (page 222): "The maximum allowed value for order is 10 or 11(corresponding to 1024 or 2048 pages), depending on the architecture.


Thanks.

You can reserve the kind of big memory at boot time.

Originally Posted by nini09 You can reserve the kind of big memory at boot time.

Thank you for your reply.

According to DD3,chapter-8:

Allocating memory at boot time is a “dirty” technique, because it bypasses all memory management policies by reserving a private memory pool. This technique is inelegant and inflexible, but it is also the least prone to failure. Needless to say, a module can’t allocate memory at boot time; only drivers directly linked to the kernel can do that.

Is this the way a video adapter driver allocates memory ?

Thanks.