Sleeping and Non-Sleeping Allocations

Unlike the Standard C Library's malloc(3C) function, the kernel memory allocator can block (or sleep), waiting until enough virtual memory is available to satisfy the client's request. This is controlled by the 'flag' parameter to kmem_alloc(9F). A call to kmem_alloc(9F), which has the KM_SLEEP flag set, can never fail; it will block forever waiting for resources to become available.