Autovacuum is using 100% CPU time in Ubuntu 16.04

Question

Running Postgres on Ubuntu 16.04 autovacuum processes are using 100% CPU after a short time.

ps aux | grep postgres

postgres  79654 72.7  0.1 402164 226580 ?       Rs   Apr17  66:48 postgres: 9.6/main: autovacuum worker process   test
postgres  82850  0.4  0.1 379972 200984 ?       Ss   Apr17   0:14 postgres: 9.6/main: autovacuum worker process   test
postgres  83444 85.5  0.1 329888 161160 ?       Rs   Apr17  41:53 postgres: 9.6/main: autovacuum worker process   test

top

 79654 postgres  20   0  402164 226580 144188 R 100.0  0.2  66:45.14 postgres
 83444 postgres  20   0  329888 161160 141916 R 100.0  0.1  41:50.45 postgres
 86969 postgres  20   0  323852 161760 151372 R 100.0  0.1   1:58.84 postgres
 86973 postgres  20   0  322976 161284 151412 R  88.2  0.1   1:24.82 postgres

The same configuration runs on Ubuntu 14.04 like a charm... Tested with PG 9.4/9.5/9.6 and postgres.conf default config. What's the matter with U16.04?

Answer 1

Interesting that nobody found the answer...

It's a glibc bug: After upgrading from Ubuntu 14.10 (glibc 2.19) to 15.04 (glibc 2.21), we are experiencing a big performance regression in one particular PostgreSQL index creation. The index creation now takes more than 10 minutes, while before it was done in about 30 seconds.

https://sourceware.org/bugzilla/show_bug.cgi?id=18441