On Sat, 2011-04-23 at 13:34 -0500, James Bottomley wrote: > This is the preliminary conversion. It's very nasty on parisc because > the memory allocation isn't symmetric anymore: under DISCONTIGMEM, we > push all memory into bootmem and then let free_all_bootmem() do the > magic for us; Urg, that's unfortunate. I bet we could fairly easily teach the bootmem allocator to allow a couple of bootmem_data's to hang off of an individual pgdat. Put each pmem_ranges in one of those instead of a pgdat. That would at least help with the bitmap size explosion and extra loops. > now we have to do separate initialisations for ranges > because SPARSEMEM can't do multi-range boot memory. It's also got the > horrible hack that I only use the first found range for bootmem. I'm > not sure if this is correct (it won't be if the first found range can be > under about 50MB because we'll run out of bootmem during boot) ... we > might have to sort the ranges and use the larges, but that will involve > us in even more hackery around the bootmem reservations code. > > The boot sequence got a few seconds slower because now all of the loops > over our pfn ranges actually have to skip through the holes (which takes > time for 64GB). Which iterations were these, btw? All of the ones I saw the patch touch seemed to be running over just a single pmem_range. > All in all, I've not been very impressed with SPARSEMEM over > DISCONTIGMEM. It seems to have a lot of rough edges (necessitating > exception code) which DISCONTIGMEM just copes with. We definitely need to look at extending it to cover bootmem-time a bit. Is that even worth it these days with the no-bootmem bits around? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>