On Fri, 6 Jul 2007, Heikki Linnakangas wrote:

There's something wrong with that. The number of buffer allocations shouldn't depend on the bgwriter strategy at all.

I was seeing a smaller (closer to 5%) increase in buffer allocations switching from no background writer to using the stock one before I did any code tinkering, so it didn't strike me as odd. I believe it's related to the TPS numbers. When there are more transactions being executed per unit time, it's more likely the useful blocks will stay in memory because their usage_count is getting tickled faster, and therefore there's less of the most useful blocks being swapped out only to be re-allocated again later.

Since the bad bgwriter tunings reduce TPS, I believe that's the mechanism by which there are more allocations needed. I'll try to keep an eye on this now that you've brought it up.

* Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com Baltimore, MD

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