> Ok, this is the best I could come up with, without some real test hardware.
>
> The only improvement I see in single-disk scenarios:
> * Huge speedup of back-sequential index-only scans
> * Marginal speedup on forward index-only scans (5% or less)
> * No discernible difference in heap-including scans (even with heap
> prefetch), but I'm pretty sure a real RAID setup would change this
> * No change in pgbench (so I guess no regression for small transactions)
If the gain is visible mostly for the backward and not for other access
patterns I suggest to check the work done in backward-prefecthing in linux.
http://thread.gmane.org/gmane.linux.kernel.mm/73837 for example
I don't know how others (BSD, windows, ...) handle this case.
Maybe the strategy to use our own prefetch is better, then I would like to use
it also in places where we used to hack to make linux understand that we will
benefits from prefetching.
--
Cédric Villemain +33 (0)6 20 30 22 52
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