Hi Hackers, This patch ensures get_database_list() switches back to the memory context in use upon entry rather than returning with TopMemoryContext as the context.
This will address memory allocations in autovacuum.c being associated with TopMemoryContext when they should not be. autovacuum.c do_start_worker() with current context 'Autovacuum start worker (tmp)' invokes get_database_list(). Upon return, the current context has been changed to TopMemoryContext by AtCommit_Memory() as part of an internal transaction. Further down in the do_start_worker(), pgstat_fetch_stat_dbentry() is invoked. Previously this didn't pose a issue, however recent changes altered how pgstat_fetch_stat_dbentry() is implemented. The new implementation has a branch utilizing palloc. The patch ensures these allocations are associated with the 'Autovacuum start worker (tmp)' context rather than the TopMemoryContext. Prior to the change, leaving an idle laptop PG instance running just shy of 3 days saw the autovacuum launcher process grow to 42MB with most of that growth in TopMemoryContext due to the palloc allocations issued with autovacuum worker startup. -- Reid Thompson Senior Software Engineer Crunchy Data, Inc. reid.thomp...@crunchydata.com www.crunchydata.com -- Reid Thompson Senior Software Engineer Crunchy Data, Inc. reid.thomp...@crunchydata.com www.crunchydata.com
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index b3b1afba86..92b1ef45c1 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -1941,6 +1941,13 @@ get_database_list(void) CommitTransactionCommand(); + /* + * CommitTransactionCommand returns with CurrentMemoryContext set + * to TopMemoryContext. Switch back to the context that we entered + * with. + */ + MemoryContextSwitchTo(resultcxt); + return dblist; }
