On 2/13/19 4:56 AM, Peter Zijlstra wrote: > > Personally I think u64 and company should already force natural > alignment; but alas. But there is an ISA/ABI angle here too. e.g. On 32-bit ARC, LDD (load double) is allowed to take a 32-bit aligned address to load a register pair. Thus all u64 need not be 64-bit aligned (unless attribute aligned 8 etc) hence the relaxation in ABI (alignment of long long is 4). You could certainly argue that we end up undoing some of it anyways by defining things like ARCH_KMALLOC_MINALIGN to 8, but still... > I though that was part of the reason we have __u64 > and co., so that ABI is invariant to kernel alignment changes. Apparently not. >>> I suspect the slab allocator should be returning 8 byte aligned addresses >>> on all systems.... >> >> why ? As I understand it is still not fool proof against the expected alignment of >> inner members. There ought to be a better way to enforce all this. > > I agree that for ARC ARCH_SLAB_MINALIGN should be at least 8. This issue aside, are there other reasons ? Because making it 8 on ARC is just pending the eventuality for later.
