Hi, We are using mpc8260 for our communication application. In our application, we have to allocate contiguous memory of size 1536 bytes. These memory will be used in the buffer descriptors for DMA. These will be later freed from another driver in the kernel. For DMA we require physically contiguous addresses.
We are currently allocating 1536 bytes using dev_alloc_skb non interrupt context and skb_alloc(x, GFP_ATOMIC) in terrupt context. The doubt is that will a dev_alloc_skb()/skb_alloc call allocate 1536 bytes within page boundary? My understanding of kmem allocation is that kernel keeps free buffers of size 512k, 256k ... (buddy system) upto 1 page, and whenver a request arises, contiguous memory is allocated from the nearest large page frame block. If there is no page frame block to satisfy this request, it will fail. In this context can I safely asssume that a dev_alloc_skb() request will return memory which is contiguous physical memory within a page ? if not what should be the approach I should take? I cannot allocate 1 page for 1536 bytes, which will cause huge over heads. shall I redefine PAGE_SIZE to 2048 and allocate one page for 1536 bytes and do a skb_put on the data? Any help is appreciated. Om. ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
