Or... It seems to me that we have been observing something on the order of 10x-20x slowdown for vacuuming a table. I think this is WAY overcompensating for the original problems, and would cause it's own problem as mentioned above. Since the granularity of delay seems to be the problem can we do more work between delays? Instead of sleeping after every page (I assume this is what it's doing) perhaps we should sleep every 10 pages,
I also think doing more than one page per sleep is advantageous since
it would still allow the OS to do it's readahead optimizations.
I suspect those would fall flat if only one page is fetched per sleep.
So maybe the setting shouldn't be "n ms wait between vacuum actions" but "vacuum pages to handle before sleeping 10 ms".
Regards, Andreas
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