我客戶的伺服器最近開始出現效能問題。伺服器上託管的單一網站載入速度非常慢。它是使用 WordPress 使用自訂主題建立的。安裝了最低數量的插件，並且在效能問題開始的最後幾週內沒有添加任何插件。
伺服器有 2 個 CPU 和 2GB 記憶體。伺服器堆疊是帶有 Ubuntu 20.04 和 PHP FPM 的 LAMP。所有安裝的軟體都保持最新。
在執行 WordPress 網站時，兩個 CPU 的使用率始終超過 80%。
free -m 指令傳回以下內容：總計 1983、已使用 1734、可用 64、分享 132、Buff/Cache 184 和可用 12。
重新啟動伺服器可以暫時解決這些問題。
安裝Redis Server用於物件快取。目前伺服器或 WordPress 中沒有安裝其他快取或優化外掛。
我運行sudo tail -n 10 /var/log/apache2/domain.com_error.log並包含了下面的輸出。
[Mon Feb 20 09:59:27.377362 2023] [proxy_fcgi:error] [pid 310468] [client 104.224.117.81:33410] AH01071: Got error 'PHP message: Predis\\Response\\ServerException: LOADING Redis is loading the dataset in memory in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php:352\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(320): Predis\\Client->onErrorResponse()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(299): Predis\\Client->executeCommand()\n#2 /var/www/example.com/wp-content/object-cache.php(562): Predis\\Client->__call()\n#3 /var/www/example.com/wp-content/object-cache.php(257): WP_Object_Cache->__construct()\n#4 /var/www/example.com/wp-includes/load.php(730): wp_cache_init()\n#5 /var/www/example.com/wp-settings.php(131): wp_start_object_cache()\n#6 /var/www/example.com/wp-config.php(109): require_once('...')\n#7 /var/www/example.com/wp-load.php(50): require_once('...')\n#8 /var/www/example.com/wp-blog-header.php(13): require_once(...', referer: https://www.example.com/listing/the-tree-corral/
[Mon Feb 20 09:59:28.858978 2023] [proxy_fcgi:error] [pid 310553] [client 157.55.39.219:22656] AH01071: Got error 'PHP message: Predis\\Connection\\ConnectionException: Connection refused [tcp://127.0.0.1:6379] in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Connection/AbstractConnection.php:132\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Connection/StreamConnection.php(109): Predis\\Connection\\AbstractConnection->onConnectionError()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Connection/StreamConnection.php(154): Predis\\Connection\\StreamConnection->createStreamSocket()\n#2 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Connection/StreamConnection.php(80): Predis\\Connection\\StreamConnection->tcpStreamInitializer()\n#3 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Connection/AbstractConnection.php(81): Predis\\Connection\\StreamConnection->createResource()\n#4 /var/www/example.com/wp-content...'
[Mon Feb 20 09:59:28.859372 2023] [proxy_fcgi:error] [pid 310553] [client 157.55.39.219:22656] AH01071: Got error 'PHP message: PHP Warning: Undefined variable $image in /var/www/example.com/wp-content/themes/themename/functions.php on line 548'
[Mon Feb 20 09:59:32.089611 2023] [proxy_fcgi:error] [pid 310501] [client 157.55.39.219:24128] AH01071: Got error 'PHP message: Predis\\Response\\ServerException: LOADING Redis is loading the dataset in memory in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php:352\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(320): Predis\\Client->onErrorResponse()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(299): Predis\\Client->executeCommand()\n#2 /var/www/example.com/wp-content/object-cache.php(562): Predis\\Client->__call()\n#3 /var/www/example.com/wp-content/object-cache.php(257): WP_Object_Cache->__construct()\n#4 /var/www/example.com/wp-includes/load.php(730): wp_cache_init()\n#5 /var/www/example.com/wp-settings.php(131): wp_start_object_cache()\n#6 /var/www/example.com/wp-config.php(109): require_once('...')\n#7 /var/www/example.com/wp-load.php(50): require_once('...')\n#8 /var/www/example.com/wp-blog-header.php(13): require_once(...'
[Mon Feb 20 09:59:32.089919 2023] [proxy_fcgi:error] [pid 310501] [client 157.55.39.219:24128] AH01071: Got error 'PHP message: PHP Warning: Undefined variable $image in /var/www/example.com/wp-content/themes/themename/functions.php on line 548'
[Mon Feb 20 09:59:32.285842 2023] [proxy_fcgi:error] [pid 310279] [client 185.191.171.4:8256] AH01071: Got error 'PHP message: Predis\\Response\\ServerException: LOADING Redis is loading the dataset in memory in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php:352\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(320): Predis\\Client->onErrorResponse()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(299): Predis\\Client->executeCommand()\n#2 /var/www/example.com/wp-content/object-cache.php(562): Predis\\Client->__call()\n#3 /var/www/example.com/wp-content/object-cache.php(257): WP_Object_Cache->__construct()\n#4 /var/www/example.com/wp-includes/load.php(730): wp_cache_init()\n#5 /var/www/example.com/wp-settings.php(131): wp_start_object_cache()\n#6 /var/www/example.com/wp-config.php(109): require_once('...')\n#7 /var/www/example.com/wp-load.php(50): require_once('...')\n#8 /var/www/example.com/wp-blog-header.php(13): require_once(...'
[Mon Feb 20 09:59:32.286079 2023] [proxy_fcgi:error] [pid 310279] [client 185.191.171.4:8256] AH01071: Got error 'PHP message: PHP Warning: Undefined variable $image in /var/www/example.com/wp-content/themes/themename/functions.php on line 548'
[Mon Feb 20 09:59:32.561144 2023] [proxy_fcgi:error] [pid 309940] [client 185.191.171.19:16376] AH01071: Got error 'PHP message: Predis\\Response\\ServerException: LOADING Redis is loading the dataset in memory in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php:352\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(320): Predis\\Client->onErrorResponse()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(299): Predis\\Client->executeCommand()\n#2 /var/www/example.com/wp-content/object-cache.php(562): Predis\\Client->__call()\n#3 /var/www/example.com/wp-content/object-cache.php(257): WP_Object_Cache->__construct()\n#4 /var/www/example.com/wp-includes/load.php(730): wp_cache_init()\n#5 /var/www/example.com/wp-settings.php(131): wp_start_object_cache()\n#6 /var/www/example.com/wp-config.php(109): require_once('...')\n#7 /var/www/example.com/wp-load.php(50): require_once('...')\n#8 /var/www/example.com/wp-blog-header.php(13): require_once(...'
[Mon Feb 20 09:59:33.157553 2023] [proxy_fcgi:error] [pid 310553] [client 157.55.39.219:22656] AH01071: Got error 'PHP message: Predis\\Response\\ServerException: LOADING Redis is loading the dataset in memory in /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php:352\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(320): Predis\\Client->onErrorResponse()\n#1 /var/www/example.com/wp-content/plugins/redis-cache/dependencies/predis/predis/src/Client.php(299): Predis\\Client->executeCommand()\n#2 /var/www/example.com/wp-content/object-cache.php(562): Predis\\Client->__call()\n#3 /var/www/example.com/wp-content/object-cache.php(257): WP_Object_Cache->__construct()\n#4 /var/www/example.com/wp-includes/load.php(730): wp_cache_init()\n#5 /var/www/example.com/wp-settings.php(131): wp_start_object_cache()\n#6 /var/www/example.com/wp-config.php(109): require_once('...')\n#7 /var/www/example.com/wp-load.php(50): require_once('...')\n#8 /var/www/example.com/wp-blog-header.php(13): require_once(...'
[Mon Feb 20 09:59:33.157733 2023] [proxy_fcgi:error] [pid 310553] [client 157.55.39.219:22656] AH01071: Got error 'PHP message: PHP Warning: Undefined variable $image in /var/www/example.com/wp-content/themes/themename/functions.php on line 548'
關於如何解決這些問題有什麼建議嗎？
我是伺服器管理員新手，但渴望學習。