Messages in this thread | | | Date | Wed, 24 Mar 2010 10:00:31 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 06/20] early_res: seperate common memmap func from e820.c to fw_memmap.cy |
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* Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> > > I though one possibility would be to have LMB regions become more lists > > than arrays, so that the static storage only needs to cover as much as > > is needed during really early boot (and we could probably still move the > > BSS top point on some archs to dynamically make more ... actually we > > could be smart arses and use LMB to allocate more LMB list heads if we > > are reaching the table limit :-) > > Actually what about that: > > LMB entries are linked-listed. The array is just storage for those entry > "heads". > > The initial static array only needs to be big enough for very very early > platform specific kernel bits and pieces, so it could even be sized by a > Kconfig option. Or it could just use a klimit moving trick to pick up a > page right after the BSS but that may need to be arch specific. > > lmb_init() queues all the entries from the initial array in a freelist > > lmb_alloc() and lmb_reserve() just pop entries from that freelist to > populate the two main linked lists (memory and reserved). > > When something tries to dequeue up the last freelist entry, then under > the hood, LMB uses it instead to allocate a new block of LMB entries > that gets added to the freelist. > > We never free blocks of LMB entries. > > That way, we can fine tine the static array to be as small as we can > realistically make it be, and we have no boundary limitations on the > amount of entries in either the memory list or the reserved list. > > I'm a bit too flat out right now to write code, but if there's no objection, > I might give that a go either later this week or next week, see if I can > replace bootmem on powerpc.
That would be fantastic! PowerPC and x86 both doing it would give it enough of a critical mass to make the removal of bootmem realistic.
Thanks,
Ingo
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