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> <86802c440805032106t4d020838v39aaf93309003cdb@mail.gmail.com> Date: Sun, 04 May 2008 10:57:11 +0200 In-Reply-To: <86802c440805032106t4d020838v39aaf93309003cdb@mail.gmail.com> (Yinghai Lu's message of "Sat, 3 May 2008 21:06:02 -0700") Message-ID: <87hcdev448.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Yinghai Lu Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andi Kleen , Andrew Morton , Linus Torvalds List-ID: Hi, "Yinghai Lu" writes: > On Sat, May 3, 2008 at 10:54 AM, Ingo Molnar wrote: >> >> * 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 ;-) > > for spanning support node0:0-2g, 4-6g; node1: 2-4g, 6-8g, could have > some problem. Could you eleborate on that? > +/* > + * rootmem_register_node - register a node to rootmem > + * @nid: node id > + * @start: first pfn on the node > + * @end: first pfn after the node > + * > + * This function must not be called anymore if the allocator > + * is already up and running (rootmem_setup() has been called). > + */ > +void __init rootmem_register_node(int nid, unsigned long start, > + unsigned long end) > +{ > + BUG_ON(rootmem_functional); > + > + if (start < rootmem_min_pfn) > + rootmem_min_pfn = start; > + if (end > rootmem_max_pfn) > + rootmem_max_pfn = end; > + > + rootmem_node_pages[nid] = end - start; > + rootmem_node_offsets[nid] = start; > + rootmem_nr_nodes++; > +} > > could change rootmem_node_pages/offsets to be struct array with > offset, pages, and nid. and every node could several struct. and whole > array should be sorted with nid. The whole point is to be agnostic about weird NUMA configs. Right now, I am pretty proud of the simple data structures and I would avoid blowing them up again unless there is a hard reason to do so. 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