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Hi, Ingo Molnar <mingo@elte.hu> writes: > * Johannes Weiner <hannes@saeurebad.de> wrote: > >> I was spending some time and work on the bootmem allocator the last >> few weeks and came to the conclusion that its current design is not >> appropriate anymore. >> >> As Ingo said in another email, NUMA technologies will become weirder, >> nodes whose PFNs span other nodes for example and it makes bootmem >> code become an unreadable mess. >> >> So I sat down two days ago and rewrote the allocator, here is the >> result: rootmem! > > hehe :-) > >> The biggest difference to the old design is that there is only one >> bitmap for all PFNs of all nodes together, so the overlapping PFN >> problems simply dissolve and fun like allocations crossing node >> boundaries work implicitely. The new API requires every node used by >> the allocator to be registered and after that the bitmap gets >> allocated and the allocator enabled. >> >> I chose to add a new allocator rather than replacing bootmem at once >> because that would have required all callsites to switch in one go, >> which would be a lot. The new allocator can be adopted more slowly >> and I added a compatibility API for everything besides actually >> setting up the allocator. When the last user dies, bootmem can be >> dropped completely (including pgdat->bdata, whee..) >> >> The main ideas from bootmem have been stolen^W preserved but the new >> design allowed me to shrink the code a lot and express things more >> simple and clear: >> >> $ sloc.awk < mm/bootmem.c >> 455 lines of code, 65 lines of comments (520 lines total) >> >> $ sloc.awk < mm/rootmem.c >> 243 lines of code, 96 lines of comments (339 lines total) > > amazing! > > i'd still suggest to keep it all named bootmem though :-/ How about > bootmem2.c and then renaming it back to bootmem.c, once the last user is > gone? That would save people from having to rename whole chapters in > entire books ;-) Hehe, I still have bootmem2.c flying around... I was not sure if the migration is easier with the same name or with a different name but the API is mostly compatible in the end, so staying with bootmem should be possible and it sounds way better... Hannes | ||||||||||||
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