tune PHP and FPM for 1-core/3GB VPS performance

Reduce FPM workers from 12 to 5 max to stop memory thrashing on
a single-core VPS with 3GB RAM. Add OPcache and APCu tuning to
reduce filesystem stat calls and improve cache hit rates.

nextcloud/docker-compose.yml

@@ -20,6 +20,7 @@ services:
       - ./hooks/post-installation.sh:/docker-entrypoint-hooks.d/post-installation/post-installation.sh:ro
       - ./hooks/post-upgrade.sh:/docker-entrypoint-hooks.d/post-upgrade/post-upgrade.sh:ro
       - ./fpm-tuning.conf:/usr/local/etc/php-fpm.d/zz-tuning.conf:ro
+      - ./php-tuning.ini:/usr/local/etc/php/conf.d/zz-tuning.ini:ro
     networks:
       - nextcloud-internal
     logging:

nextcloud/fpm-tuning.conf

@@ -1,7 +1,7 @@
 [www]
 pm = dynamic
-pm.max_children = 12
-pm.start_servers = 4
-pm.min_spare_servers = 2
-pm.max_spare_servers = 6
+pm.max_children = 5
+pm.start_servers = 2
+pm.min_spare_servers = 1
+pm.max_spare_servers = 3
 pm.max_requests = 500

nextcloud/php-tuning.ini

@@ -0,0 +1,10 @@
+; OPcache tuning for Nextcloud
+opcache.interned_strings_buffer=16
+opcache.max_accelerated_files=10000
+opcache.revalidate_freq=60
+opcache.save_comments=1
+opcache.enable_file_override=1
+
+; APCu local cache
+apc.shm_size=64M
+apc.enable_cli=1