matrix: Retune PostgreSQL again

Bump the mem settings higher again, now that we know they're not the
cause. Also increase the maximum connection count.

playbooks/matrix.archlinux.org.yml

@@ -15,8 +15,8 @@
     - { role: nginx }
     - role: postgres
       postgres_shared_buffers: 1GB
-      postgres_work_mem: 32MB
-      postgres_maintenance_work_mem: 32MB
+      postgres_work_mem: 64MB
+      postgres_maintenance_work_mem: 256MB
       postgres_effective_cache_size: 2GB
       postgres_jit: 'off'
     - role: postfix

roles/matrix/templates/homeserver.yaml.j2

@@ -761,8 +761,8 @@ database:
     dbname: synapse
     user: synapse
     password: {{ vault_postgres_users.synapse }}
-    cp_min: 3
-    cp_max: 3
+    cp_min: 1
+    cp_max: 5
 
 
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