Thread

1. pg_test_fsync output and commit_delay

   Peter Geoghegan <peter@2ndquadrant.com> — 2012-09-08T21:26:21Z

   I propose that we try and develop better commit_delay advice, to make
   it easier to set the parameter in a way that actually helps
   performance. I have been researching a way to make commit_delay
   adaptive, though have yet to develop any further insight that is worth
   sharing. This may change.
   
   The attached simple patch alters the output produced by pg_test_fsync,
   so that we also see the average sync time per op. The pg_test_fsync
   docs have had minor alterations too. Hopefully, another doc patch will
   follow that builds upon this, and actually firmly recommends taking a
   particular course of action when setting commit_delay - my previous
   observations about what helped throughput, though supported by Greg
   Smith, have not been scrutinised enough just yet, I feel. For now, the
   equivocated wording of my doc alterations (that raw wal_sync_method
   file sync time might *somehow* be useful here) seems appropriate.
   
   -- 
   Peter Geoghegan       http://www.2ndQuadrant.com/
   PostgreSQL Development, 24x7 Support, Training and Services
   

2. Re: pg_test_fsync output and commit_delay

   Josh Berkus <josh@agliodbs.com> — 2012-09-08T22:27:33Z

   > The attached simple patch alters the output produced by pg_test_fsync,
   > so that we also see the average sync time per op. 
   
   Good idea.  A median would be even better, but harder to calculate, I
   imagine.  You might consider providing a maximum, too.
   
   > The pg_test_fsync
   > docs have had minor alterations too. Hopefully, another doc patch will
   > follow that builds upon this, and actually firmly recommends taking a
   > particular course of action when setting commit_delay - my previous
   > observations about what helped throughput, though supported by Greg
   > Smith, have not been scrutinised enough just yet, I feel. For now, the
   > equivocated wording of my doc alterations (that raw wal_sync_method
   > file sync time might *somehow* be useful here) seems appropriate.
   
   I'll see what I can do.
   
   -- 
   Josh Berkus
   PostgreSQL Experts Inc.
   http://pgexperts.com