Re: [RFC] Arch option to touch newly allocated pages

Andrew Morton
2002-03-07T22:25:30Z

Rik van Riel wrote:
>
> > So what *is* a solution. Well, there's only so much memory available.
> > In either case a) or case b) we're "fairly" distributing that memory
> > between all files. And that's the problem. *All* the files have too
> > small a readahead window. Which points one at: we need to stop being
> > fair. We need to give some files a good readahead window and others
> > not. The "soft pinning" which I propose with GFP_READAHEAD and
> > PG_readhead might have that effect, I think.
>
> Actually, it could boil down to something more:
>
> use-once reduces the VM to FIFO order, which suffers from
> belady's anomaly so it doesn't matter much how much memory
> you throw at it
>
> drop-behind will suffer the same problem once the readahead
> memory is too large to keep in the system, but at least the
> already-used pages won't kick out readahead pages

err.. Was there a fix in there somewhere, or are we stuck?

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