Re: [discuss] Re: 32-bit dma allocations on 64-bit platforms

[William Lee Irwin III <wli@holomorphy.com>]

On Thu, Jun 24, 2004 at 07:39:27PM +0200, Andrea Arcangeli wrote:
> I looked more into it and you can leave it turned off since it's not
> going to work.
> it's all in functions of z->pages_* and those are _global_ for all the
> zones, and in turn they're absolutely meaningless.
> the algorithm has nothing in common with lowmem_reverse_ratio, the
> effect has a tinybit of similarity but the incremntal min thing is so
> weak and so bad that it will either not help or it'll waste tons of
> memory. Furthemore you cannot set a sysctl value that works for all
> machines. The whole thing should be dropped and replaced with the fine
> production quality lowmem_reserve_ratio in 2.4.26+
> (the only broken thing of lowmem_reserve_ratio is that it cannot be
> tuned, not even at boottime, a recompile is needed, but that's fixable
> to tune it at boot time, and in theory at runtime too, but the point is
> that no dyanmic tuning is required with it)
> Please focus on this code of 2.4:

There is mention of discrimination between pinned and unpinned
allocations not being possible; I can arrange this for more
comprehensive coverage if desired. Would you like this to be arranged,
and if so, how would you like that to interact with the fallback
heuristics?


-- wli