Messages in this thread | | | Date | Fri, 14 Jan 2000 03:13:48 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: [RFC] 2.3.39 zone balancing |
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On Thu, 13 Jan 2000, Linus Torvalds wrote:
> HOWEVER, I don't think this is going to be a huge issue in most cases. And > if people don't need non-DMA memory, then the pages we "swapped" out are > going to stay in RAM anyway, so it's not going to hurt us. > > Anyway, I obviously do agree that I may well be wrong, and that real life > is going to come back and bite us, and we'll end up having to not do it > this way. However, I'd prefer trying the "conceptually simple" path first, > and only if it turns out that yes, I was completely wrong, do we try to > fix it up with magic heuristics etc.
hm., i think we'll see this with ISA soundcards (still the majority) if used as modules. Right now kswapd just gives up too easy and says 'no such page', on a box with lots of RAM and all DMA allocated in process VM space.
Anyway, the patch and suggestion of passing in a single zone is i believe completely wrong, because it advances mm->swap_address, which unfairly selects a given range to be checked for only one zone. So i think it's either zone-bitmaps (or equivalent multi-zone logic) or what you suggested, to have no zone-awareness in swap_out() for now at all.
(i believe this is also going to bite us with the IA64 port - kswapd will have no information to free pages from the right node, we could solve this already with a zone bitmap, or by starting per-zone kswapds. The latter one looks like overkill to me, but it's conceptually cleaner than bitmaps and and does not have a limitation on the number of zones. Might not be a highprio issue though.)
-- mingo
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