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From: Anton Yuzhaninov <[email protected]>
To: [email protected]
Subject: number of semaphores and semaphore sets
Date: Mon, 21 Mar 2011 19:05:12 +0300
Message-ID: <[email protected]> (raw)

This page:
http://www.postgresql.org/docs/9.0/interactive/kernel-resources.html

has formula:
ceil((max_connections + autovacuum_max_workers) / 16)

for number of semaphore sets (identifiers).

It seems to be wrong (outdated).

Correct formula seems to be

ceil((max_connections + autovacuum_max_workers + 4) / 16)

Semaphore sets created in src/backend/storage/lmgr/proc.c:
1. MaxConnections
2. autovacuum_max_workers + 1
3. NUM_AUXILIARY_PROCS (currently 3)

-- 
  Anton Yuzhaninov

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