On Tue, 2014-04-08 at 12:47 -0700, Dave Hansen wrote: > On 04/08/2014 11:23 AM, Nathan Fontenot wrote: > > On 04/08/2014 11:13 AM, Dave Hansen wrote: > >> On 04/08/2014 01:27 AM, Li Zhong wrote: > >>> If Dave and others don't have further objections, it seems this small > >>> userspace incompatibility could be accepted by most of us, and I don't > >>> need to make a version 2. > >> > >> Let me ask another question then. What are the units of > >> phys_index/end_phys_index? How do we expose those units to userspace? > >> > > > > The documentation for these files just states that the files contain > > the first and last section id of memory in the memory block for > > phys_index and end_phys_index respectively. > > > > I'm not sure the values have ever been units of anything, at least not > > that I remember. > > <sigh> > > There are two units. SECTION_SIZE, which is completely internal to the > kernel, and block_size_bytes which used to be the same as SECTION_SIZE, > but is not now. Which one of those two is phys_index/end_phys_index in, > and if it is in terms of SECTION_SIZE like this patch proposes, how do > we tell userspace how large SECTION_SIZE is?
With this patch, I think we could still tell how large SECTION_SIZE is. block_size_bytes tells us the size of the block, and end_phys_index-phys_index+1, tells us the numbers of sections in the block, and then we could know the SECTION_SIZE by a division. Not that obvious, but if needed, we could easily add a file telling us section_size or sections_per_block. > > block_size_bytes is supposed to tell you how large the sections are. In > the case where we lumped a bunch of sections together, we also bumped up > block_size_bytes. That's why we currently divide the *ACTUAL* section > number in phys_index/end_phys_index by block_size_bytes. > > That document really needs to be updated to stop referring to sections > (at least in the descriptions of the user interface). We can not change > the units of phys_index/end_phys_index without also changing > block_size_bytes. How about adding a new section_size_bytes together with this patch? Or do you mean we don't need to expose any information related to SECTION to userspace? Thanks, Zhong -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
