Re: Lockless StrategyGetBuffer() clock sweep

On 2014-12-10 21:52:17 -0500, Robert Haas wrote:
> Maybe you could store the pgprocno instead of the PROC *.

That's a good idea. Here's a patch implementing that and other things.

Changes:
* The handling of wraparound is slight changed. There's a separate patch
  for the case where nextVictimBuffer is above NBuffers. That allows a)
  to avoid the somewhat expensive modulo operation in the common case b)
  always consistent results for StrategySyncStart()
* StrategySyncStart() doesn't have a situation in which it can return
  inaccurate information anymore. That could actually trigger an
  assertion bgwriter.
* There was a bug because the local victim variable was signed instead
  of unsigned.
* Clock sweep ticks are moved into a separate routine.

Comments?

Greetings,

Andres Freund

--
 Andres Freund                       http://www.2ndQuadrant.com/
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