Re: Need help identifying a periodic performance issue.

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On Nov 17, 2021, at 10:51 AM, Robert Creager <robertc@xxxxxxxxxxxxxxxx> wrote:



On Nov 15, 2021, at 10:50 PM, Thomas Munro <thomas.munro@xxxxxxxxx> wrote:

This message originated outside your organization.

On Tue, Nov 16, 2021 at 5:43 PM Robert Creager <robertc@xxxxxxxxxxxxxxxx> wrote:
One CPU is pegged, the data has been sent over STDIN, so Postgres is not waiting for more, there are no other queries running using this select:

So PostgreSQL is eating 100% CPU, with no value shown in
wait_event_type, and small numbers of system calls are counted.  In
that case, is there an interesting user stack that jumps out with a
profiler during the slowdown (or the kernel version, stack())?

sudo dtrace -n 'profile-99 /arg0/ { @[ustack()] = count(); } tick-10s
{ exit(0); }

Ok, here is the logs around a dtrace included.  I have dtaces every 1m10s, and the two I looked at, the last entry, were the same.

Also, the wall settings are different on this machine, had changed them on the original email submittal to see if it was related.

tapesystem=# SELECT name, current_setting(name), source
  FROM pg_settings
  WHERE source NOT IN ('default', 'override');
              name               |         current_setting         |       source       
---------------------------------+---------------------------------+--------------------
 application_name                | psql                            | client
 autovacuum_analyze_scale_factor | 0.05                            | configuration file
 autovacuum_analyze_threshold    | 5000                            | configuration file
 autovacuum_max_workers          | 8                               | configuration file
 autovacuum_vacuum_cost_delay    | 5ms                             | configuration file
 autovacuum_vacuum_scale_factor  | 0.1                             | configuration file
 autovacuum_vacuum_threshold     | 5000                            | configuration file
 checkpoint_completion_target    | 0.9                             | configuration file
 checkpoint_timeout              | 15min                           | configuration file
 client_encoding                 | UTF8                            | client
 DateStyle                       | ISO, MDY                        | configuration file
 default_text_search_config      | pg_catalog.english              | configuration file
 dynamic_shared_memory_type      | posix                           | configuration file
 effective_cache_size            | 6546MB                          | configuration file
 effective_io_concurrency        | 200                             | configuration file
 full_page_writes                | off                             | configuration file
 hot_standby                     | off                             | configuration file
 lc_messages                     | C                               | configuration file
 lc_monetary                     | C                               | configuration file
 lc_numeric                      | C                               | configuration file
 lc_time                         | C                               | configuration file
 listen_addresses                | *                               | configuration file
 log_autovacuum_min_duration     | 1s                              | configuration file
 log_checkpoints                 | on                              | configuration file
 log_connections                 | on                              | configuration file
 log_destination                 | syslog                          | configuration file
 log_disconnections              | on                              | configuration file
 log_duration                    | off                             | configuration file
 log_line_prefix                 | db=%d,user=%u,app=%a,client=%h  | configuration file
 log_lock_waits                  | on                              | configuration file
 log_min_duration_sample         | 500ms                           | configuration file
 log_min_duration_statement      | 1s                              | configuration file
 log_statement_sample_rate       | 0.01                            | configuration file
 log_temp_files                  | 0                               | configuration file
 log_timezone                    | UTC                             | configuration file
 maintenance_work_mem            | 1964MB                          | configuration file
 max_connections                 | 250                             | configuration file
 max_parallel_workers_per_gather | 8                               | configuration file
 max_replication_slots           | 0                               | configuration file
 max_stack_depth                 | 32MB                            | configuration file
 max_wal_senders                 | 0                               | configuration file
 max_wal_size                    | 10GB                            | configuration file
 max_worker_processes            | 8                               | configuration file
 random_page_cost                | 2                               | configuration file
 shared_buffers                  | 22064MB                         | configuration file
 synchronous_commit              | off                             | configuration file
 temp_buffers                    | 654MB                           | configuration file
 TimeZone                        | UTC                             | configuration file
 track_activities                | on                              | configuration file
 track_counts                    | on                              | configuration file
 update_process_title            | off                             | configuration file
 vacuum_cost_delay               | 1ms                             | configuration file
 wal_init_zero                   | off                             | configuration file
 wal_level                       | minimal                         | configuration file
 wal_recycle                     | off                             | configuration file
 work_mem                        | 654MB                           | configuration file


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