Re: Good and bad news on 2.1.110, and a fix

[Rik van Riel <H.H.vanRiel@phys.uu.nl>]

On Thu, 23 Jul 1998, Bill Hawes wrote:
> Stephen C. Tweedie wrote:
>  
> > The patch to page_alloc.c is a minimal fix for the fragmentation
> > problem.  It simply records allocation failures for high-order pages,
> > and forces free_memory_available to return false until a page of at
> > least that order becomes available.  The impact should be low, since

This sound suspiciously like the first version of
free_memory_available() that Linus introduced in
2.1.89...

> One possible downside is that kswapd infinite looping may become more
> likely, as we still have no way to determine when the memory

It will happen for sure; just think of what will happen
when that 64 kB DMA allocation fails on your 6 MB box :(

We saw the results in 2.1.89 and I don't see any reason
to repeat the experiments now, at least not until Bill's
patch for freeing inodes is merged...

> configuration makes it impossible to achieve the memory goal. I still
> see this "swap deadlock" in 110 (and all recent kernels) under low
> memory or by doing a swapoff. Any ideas on how to best determine an
> infeasible memory configuration?

Well, freepages.high should be a nice hint as to when to
stop; unfortunately it is used now instead of fragmentation
issues.

Maybe we want to count the number of order-3 memory structures
free and keep that number above a certain level (back to
Zlatko's 2.1.59 patch :-).

Rik.
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