On Mon, 2010-08-16 at 09:34 -0500, Nathan Fontenot wrote: > > It's not an unresolvable issue, as this is a must-fix problem. But you > > should tell us what your proposal is to prevent breakage of existing > > installations. A Kconfig option would be good, but a boot-time kernel > > command line option which selects the new format would be much better. > > This shouldn't break existing installations, unless an architecture chooses > to do so. With my patch only the powerpc/pseries arch is updated such that > what is seen in userspace is different. Even if an arch defines the override for the sysfs dir size, I still don't think this breaks anything (it shouldn't). We move _all_ of the directories over, all at once, to a single, uniform size. The only apparent change to a user moving kernels would be a larger block_size_bytes (which is certainly not changing the ABI) and a new sysfs file for the end of the section. The new sysfs file is _completely_ redundant at this point. The architecture is only supposed to bump up the directory size when it *KNOWS* that all operations will be done at the larger section size, such as if the specific hardware has physical DIMMs which are much larger than SECTION_SIZE. Let's say we have a system with 20MB of memory, SECTION_SIZE of 1MB and a sysfs dir size of 4MB. Before the patch, we have 20 directories: one for each section. After this patch, we have 5 directories. The thing that I think is the next step, but that we _will_ probably need eventually is this, take the 5 sysfs dirs in the above case: 0->3, 4->7, 8->11, 12->15, 16->19 and turn that into a single one: 0->19 *That* will require changing the ABI, but we could certainly have some bloated and slow, but backward-compatible mode. -- 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>