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Date: Thu, 22 May 2008 02:33:45 +0200 From: Johannes Weiner <hannes@...urebad.de> To: Andrew Morton <akpm@...ux-foundation.org> Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, andi@...stfloor.org, yhlu.kernel@...il.com, ralf@...ux-mips.org, rth@...ddle.net, rmk@....linux.org.uk, tony.luck@...el.com, takata@...ux-m32r.org, geert@...ux-m68k.org, kyle@...isc-linux.org, paulus@...ba.org, lethal@...ux-sh.org, davem@...emloft.net Subject: Re: [RFC 0/3] bootmem rewrite Hi Andrew, Andrew Morton <akpm@...ux-foundation.org> writes: > On Wed, 21 May 2008 03:37:35 +0200 > Johannes Weiner <hannes@...urebad.de> wrote: > >> Hi, >> >> This is a complete overhaul of the bootmem allocator while preserving >> its original functionality, excluding bugs. > > Where angels fear to tread. Anyone who has seen this code realizes that this kind of advertisment is essential to get people looking at patches for it ;) >> free_bootmem and reserve_bootmem become a bit stricter than they are >> right now, callsites have to make sure that the PFN range is >> contiguous but it might go across node boundaries. >> >> alloc_bootmem satisfying the allocation goal is more likely as the >> routines will try to allocate on the node holding the goal first >> before falling back as opposed to the original behaviour that >> satisfies the goal only if it is on the first node. >> >> All in all, I think the code has become simpler and cleaner. All >> public interfaces have been documented, too. >> >> The first patch moves the bootmem node descriptor definitions into >> bootmem.c where they belong. >> >> The second patch is the new allocator itself. >> >> The third patch converts all users of ->node_boot_start to >> ->node_min_pfn as this is what they really use. It then removes the >> unused ->node_boot_start. >> >> Compile and runtime tested on X86_32, therefor RFC only. >> >> arch/alpha/mm/numa.c | 8 +- >> arch/arm/mm/discontig.c | 34 +- >> arch/arm/plat-omap/fb.c | 4 +- >> arch/avr32/mm/init.c | 3 +- >> arch/ia64/mm/discontig.c | 30 +- >> arch/m32r/mm/discontig.c | 4 +- >> arch/m32r/mm/init.c | 4 +- >> arch/m68k/mm/init.c | 4 +- >> arch/mips/sgi-ip27/ip27-memory.c | 3 +- >> arch/mn10300/mm/init.c | 6 +- >> arch/parisc/mm/init.c | 3 +- >> arch/powerpc/mm/numa.c | 3 +- >> arch/sh/mm/init.c | 2 +- >> arch/sh/mm/numa.c | 5 +- >> arch/sparc64/mm/init.c | 3 +- >> arch/x86/mm/discontig_32.c | 3 +- >> arch/x86/mm/numa_64.c | 6 +- >> include/linux/bootmem.h | 115 ++--- >> mm/bootmem.c | 914 +++++++++++++++++++------------------- >> mm/page_alloc.c | 4 +- > > Oh gee. Okay, seeing it again it looks a bit brutal. But it's not. The basic principles are the same, it's not that I completely changed the implementation. Okay, perhaps I did. And the arch changes are trivial. > bootmem is an area where large numbers of people have done hit-and-run > jobs over a lot of years. Nobody owns it and I'm sure that you are now > the world's expert. We just need to push ahead with this, I guess. > > I expect there will be problems - so many architectures which do such > different things, and all the configuration options churning things > around. I expect problems too. I just can not go any further with it on the resources I have. > So how to move ahead with this? > > - I think I'd prefer not to drop > > mm-fix-free_all_bootmem_core-alignment-check.patch > mm-normalize-internal-argument-passing-of-bootmem-data.patch > mm-unexport-__alloc_bootmem_core.patch > > because those are small, simple things which are on track for > 2.6.27 whereas a massive rewrite may take longer to get merged, and > may never get there at all, in which case we lost those little > fixes. I can see that. > - It would suit my purposes to have these patches right at the tail > of the -mm patch queue so that I can drop them easily if problems > occur, and so that others can revert them easily when diagnosing > problems. Good. > - It would be nice to get some review attention from architecture > guys, but I can understand them finding other things to do, when > bootmem is presumably good-enough-for-now. > > - Is x86_32 the only test platform which you have available? Awkward. Yes, unfortunately. Hardware offers via private mail, please! > Anyway, if you can redo these patches against most-recent-mm or, > better, against http://userweb.kernel.org/~akpm/mmotm then it would > make things easier for me to handle. I can then at least test it all > on my seven-odd test boxes. Please feel free to ping me if you want a > single rolled-up patch - that's always trivial and I can do it in three > minutes. I guess I just apply the quilt series to the tree you forked off? > Finally, if you haven't done so, I'd encourage you to stuff as many > handy debugging printks into this code as you possibly can. Just fill > 'er up with them. So that when people start running it and it goes > boom, they can send you their debug output _without_ having to go > through another handful of email-email-patch-rebuild-retest cycles. We > can pull them all out later on. Okay, I will make it gossip and send you a -mmotm-based version of it. Hannes -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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