pgsql: Avoid acquiring spinlock when checking if recovery has finished, - Mailing list pgsql-committers

Avoid acquiring spinlock when checking if recovery has finished, for speed.

RecoveryIsInProgress() can be called very frequently. During normal
operation, it just checks a backend-local variable and returns quickly,
but during hot standby, it checks a spinlock-protected shared variable.
Those spinlock acquisitions can become a point of contention on a busy
hot standby system.

Replace the spinlock acquisition with a memory barrier.

Per discussion with Andres Freund, Ants Aasma and Merlin Moncure.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/1a3d104475ce01326fc00601ed66ac4d658e37e5

Modified Files
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src/backend/access/transam/xlog.c |   21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)