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| author | Heikki Linnakangas <heikki.linnakangas@iki.fi> | 2015-02-23 18:53:02 +0200 |
|---|---|---|
| committer | Heikki Linnakangas <heikki.linnakangas@iki.fi> | 2015-02-23 18:53:02 +0200 |
| commit | 88e982302684246e8af785e78a467ac37c76dee9 (patch) | |
| tree | fd2f39328f140a3ffe28cedd47232be2aaeb79c2 /src/backend/postmaster/checkpointer.c | |
| parent | 0fec000365c25fd89ea583673de226e816dba60f (diff) | |
| download | postgresql-88e982302684246e8af785e78a467ac37c76dee9.tar.gz postgresql-88e982302684246e8af785e78a467ac37c76dee9.zip | |
Replace checkpoint_segments with min_wal_size and max_wal_size.
Instead of having a single knob (checkpoint_segments) that both triggers
checkpoints, and determines how many checkpoints to recycle, they are now
separate concerns. There is still an internal variable called
CheckpointSegments, which triggers checkpoints. But it no longer determines
how many segments to recycle at a checkpoint. That is now auto-tuned by
keeping a moving average of the distance between checkpoints (in bytes),
and trying to keep that many segments in reserve. The advantage of this is
that you can set max_wal_size very high, but the system won't actually
consume that much space if there isn't any need for it. The min_wal_size
sets a floor for that; you can effectively disable the auto-tuning behavior
by setting min_wal_size equal to max_wal_size.
The max_wal_size setting is now the actual target size of WAL at which a
new checkpoint is triggered, instead of the distance between checkpoints.
Previously, you could calculate the actual WAL usage with the formula
"(2 + checkpoint_completion_target) * checkpoint_segments + 1". With this
patch, you set the desired WAL usage with max_wal_size, and the system
calculates the appropriate CheckpointSegments with the reverse of that
formula. That's a lot more intuitive for administrators to set.
Reviewed by Amit Kapila and Venkata Balaji N.
Diffstat (limited to 'src/backend/postmaster/checkpointer.c')
| -rw-r--r-- | src/backend/postmaster/checkpointer.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c index cfad08d5528..0dce6a8ffaa 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -471,7 +471,7 @@ CheckpointerMain(void) "checkpoints are occurring too frequently (%d seconds apart)", elapsed_secs, elapsed_secs), - errhint("Consider increasing the configuration parameter \"checkpoint_segments\"."))); + errhint("Consider increasing the configuration parameter \"max_wal_size\"."))); /* * Initialize checkpointer-private variables used during @@ -749,11 +749,11 @@ IsCheckpointOnSchedule(double progress) return false; /* - * Check progress against WAL segments written and checkpoint_segments. + * Check progress against WAL segments written and CheckPointSegments. * * We compare the current WAL insert location against the location * computed before calling CreateCheckPoint. The code in XLogInsert that - * actually triggers a checkpoint when checkpoint_segments is exceeded + * actually triggers a checkpoint when CheckPointSegments is exceeded * compares against RedoRecptr, so this is not completely accurate. * However, it's good enough for our purposes, we're only calculating an * estimate anyway. |