From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [RFC 0/2] Rootmem: boot-time memory allocator References: <20080503152502.191599824@symbol.fehenstaub.lan> <20080503175426.GB5292@elte.hu> Date: Sun, 04 May 2008 10:54:45 +0200 In-Reply-To: <20080503175426.GB5292@elte.hu> (Ingo Molnar's message of "Sat, 3 May 2008 19:54:26 +0200") Message-ID: <87lk2qv48a.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andi Kleen , Andrew Morton , Linus Torvalds List-ID: Hi, Ingo Molnar writes: > * Johannes Weiner 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org