On Tue, Jul 30, 2002 at 09:21:57AM -0700, Martin J. Bligh wrote:

Would it not be easier to actually calculate (statistically) the 
read-ahead window, rather than actually tweaking it empirically?
If we're getting misses, there could be at least two causes - 

I wonder where these stats should really be kept. They seem to be in
the vma which probably doesn't fly too well when 20K threads are
pounding on different chunks of the same thing. Each could do locally
sequential reads and look random to the perspective of per-vma stats.

This probably gets worse if different threads are stomping in different
patterns, e.g. one sequential, one random. They also seem to lack any
way to cooperate since the hints are kept per-vma. It's also probably
easier to predict the behavior of a single task.


Cheers,
Bill
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