On Wed, 2010-09-22 at 13:40 -0500, Nathan Fontenot wrote: > On 09/22/2010 10:20 AM, Dave Hansen wrote: > > and phys_index's calculation needs to be: > > > > mem->start_phys_index * SECTION_SIZE / memory_block_size_bytes() > > I'm not sure if I follow where you suggest using this formula. Is this > instead of what is used now, the base_memory_block_id() calculation? > > If so, then I'm not sure it would work. The formula used in base_memory_block_id() > is done because the memory sections are not guaranteed to be added to the > memory block starting with the first section of the block. > > If you meant somewhere else let me know. My point was just that if we change the "block_size_bytes" contents, then we have to scale down the "memoryXXXX/phys_index" by that same amount. It *used* to be in numbers of SECTION_SIZE units, and I think it still is: - mem->start_phys_index = __section_nr(section); + mem->start_phys_index = base_memory_block_id(__section_nr(section)); + mem->end_phys_index = mem->start_phys_index + sections_per_block - 1; but now it needs to be changed to be in memory_block_size_bytes() units, *NOT* SECTION_SIZE units. Let's say we have a system with 4 16MB sections starting at 0x0. Before, we would have: block_size_bytes: 16777216 memory0/phys_index: 0 memory1/phys_index: 1 memory2/phys_index: 2 memory3/phys_index: 3 Now, we change memory_block_size_bytes() to be 32MB instead. We reduce the number of sections in half, and I think the right thing to get is: block_size_bytes: 33554432 memory0/phys_index: 0 memory1/phys_index: 1 I think, with your code (as it stands in these patches, no fixes) that we'd instead get this: block_size_bytes: 16777216 memory0/phys_index: 0 memory1/phys_index: 2 Without consulting "end_phys_index" (which isn't and can't be a part of the existing ABI), we'd think that we have two 16MB banks instead of four. -- Dave -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>