Re: [PATCH 1/9] readahead: introduce PG_readahead

[Andrew Morton]

On Sat, 19 May 2007 13:35:01 +0200 Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:

> > We have the advantage that if the kernel very occasionally gets the wrong
> > result for PageReadahead(page), nothing particularly bad will happen, so we
> > can do racy things.
>  
> On 64bit there is no particular shortage of page flags.

I think pretty much all of the upper 32 bits got used for ia64 fields,
but it's never been very clear how many were actually used or needed.

> If you ever do racy things please do them 32bit only.

hrm.  It *really* won't matter if we make one suboptimal readahead decision
every second day.  And there's value in having the same behaviour on all
architectures.

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