"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
The advantage of using a counter instead of a simple active bit is that buffers that are (or have been) used heavily will be able to go through several sweeps of the clock before being freed. Infrequently used buffers (such as those from a vacuum or seq. scan), would get marked as inactive the first time they were hit by the clock hand.
What I'm envisioning is that pinning (actually unpinning) a buffer increments the counter (up to some limit), and the clock sweep decrements it (down to zero), and only buffers with count zero are taken by the sweep for recycling.
Would there be any value in incrementing by 2 for index accesses and 1 for seq-scans/vacuums? Actually, it should probably be a ratio based on random_page_cost shouldn't it?
-- Richard Huxton Archonet Ltd
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