On Fri, 2011-04-22 at 13:24 -0700, Dave Hansen wrote: > On Fri, 2011-04-22 at 13:19 -0500, James Bottomley wrote: > > I looked at converting parisc to sparsemem and there's one problem that > > none of these cover. How do you set up bootmem? If I look at the > > examples, they all seem to have enough memory in the first range to > > allocate from, so there's no problem. On parisc, with discontigmem, we > > set up all of our ranges as bootmem (we can do this because we > > effectively have one node per range). Obviously, since sparsemem has a > > single bitmap for all of the bootmem, we can no longer allocate all of > > our memory to it (well, without exploding because some of our gaps are > > gigabytes big). How does everyone cope with this (do you search for > > your largest range and use that as bootmem or something)? > > Sparsemem is purely post-bootmem. It doesn't deal with sparse > bootmem. :( Well, this is enabled in discontigmem, sigh. > That said, I'm not sure you're in trouble. One bit of bitmap covers 4k > (with 4k pages of course) of memory, one byte covers 32k, and A 32MB > bitmap can cover 1TB of address space. It explodes, but I think it's > manageable. It hasn't been a problem enough up to this point to go fix > it. I think the platform limited physical address range is 42 bits, so I suppose that's 128MB ... hopefully we should have that as a contiguous range from the end of the loaded kernel. We're lucky they didn't enable the full ZX1 address range; that would have been 48 bits (or a whole gigabyte just for the bitmap). James -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>