Yes, I expected that to be a relatively rare case however - block
aligned transfers are much more common, and when we have multiple
blocks per page we may well want the page to go onto the active list
because there may be quite a delay between successive block accesses.
To fix this properly I suspect that just a few microseconds is enough
delay to pick up the temporal groupings you're talking about. That's
not hard to achieve.
> Preferably we'd want to have a "new" list of, say, 5% maximum
> of RAM size, where all references to a page are ignored. Any
> references made after the page falls off that list would be
> counted for page replacement purposes.
At that size you'd run a real risk of missing the tell-tale multiple
references that mark a page as frequently used. Think about metadata
here (right now, that usually just means directory pages, but later...
who knows). Once somebody has looked at two files in a directory -
while the page sits on the "ignore" list - chances are very good
they'll look at a third, but perhaps not before it drops off the south
end of the inactive queue.
Well, theorizing can only get us so far before we need to take actual
measurements.
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