What is Vmalloc area?

The functions vmalloc(), vmalloc_dma() and vmalloc_32() are provided to allocate a memory area that is contiguous in virtual address space. They all take a single parameter size which is rounded up to the next page alignment. They all return a linear address for the new allocated area.

What is Vmalloc Linux?

vmalloc is the other call to allocate memory in kernel space as like kmalloc. vmalloc allocates contiguous memory in virtual memory but it doesn’t guarantee that memory allocated in physical memory will be contiguous. Vmalloc is declared in . usage of vmalloc call is similar to malloc call.

Can Kmalloc return null?

For most kernel allocations, however, kmalloc() is the preferred interface. The function returns a pointer to a region of memory that is at least size bytes in length. The region of memory allocated is physically contiguous. On error, it returns NULL.

How do you free memory allocated by Kmalloc?

You can use kvfree() for the memory allocated with kmalloc , vmalloc and kvmalloc . The slab caches should be freed with kmem_cache_free() . And don’t forget to destroy the cache with kmem_cache_destroy().

What is Ioremap in Linux?

ioremap() function is used to map the physical addres of an I/O device to the kernel virtual address. Kernel creates a page table i.e mapping of virtual address to the physical address requested. When we do iounmap() this mapping is destroyed.

What is Kzalloc in Linux?

kzalloc — allocate memory. The memory is set to zero. kzalloc_node — allocate zeroed memory from a particular memory node.

Can Kmalloc fail?

The allocation cannot fail. The allocator will never retry if the allocation fails.

Does malloc use Kmalloc?

malloc uses Buddy algorithm for allocation of chunks. The kmalloc kernel service, which allocates physically contiguous memory regions in the kernel address space, is in built on top of the slab and object cache interface which uses slab allocator algorithm.

Does Kmalloc return contiguous memory?

The kmalloc() function returns physically and therefore virtually contiguous memory. This is a contrast to user space’s malloc() function, which returns virtually but not necessarily physically contiguous memory.