Messages in this thread | | | Date | Sat, 3 May 2008 19:54:26 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC 0/2] Rootmem: boot-time memory allocator |
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* 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 ;-)
Ingo
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