{"id":1104,"date":"2011-07-02T16:33:38","date_gmt":"2011-07-02T14:33:38","guid":{"rendered":"http:\/\/oldblogs.uct.ac.za\/blog\/big-bytes\/2011\/07\/02\/memory-issues"},"modified":"2022-09-26T20:02:18","modified_gmt":"2022-09-26T18:02:18","slug":"memory-issues","status":"publish","type":"post","link":"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/","title":{"rendered":"Memory issues"},"content":{"rendered":"We're currently investigating a memory issue with some of the worker nodes.\u00a0 Memory is not being freed up after jobs complete.\r\n\r\nUPDATE - 4 July:\r\n\r\nTurns out it's not a memory error.\u00a0 The problem is the way that net-snmp monitors and returns memory information.\u00a0 Unfortunately net-snmp clumps both real and cached memory together, so over time it looks as if memory available drops to zero.\u00a0 <a href=\"http:\/\/thwack.com\/forums\/48\/network-management\/9\/orion-network-performance-monitor\/18337\/linux-netsnmp-memory-usage-sh\/\">See this post for more info<\/a>.\u00a0 In order to fix this some jiggery-pokery may be required.\r\n\r\nUPDATE - 5 July:\r\n\r\nThe issue is now resolved.\u00a0 By creating a custom snmp OID with a perl script which gets its information straight from \/etc\/proc we can get a far better idea of actual memory in use.\u00a0 This is displayed on the dashboard and also tracked in real time by our monitoring systems.\r\n\r\n<img src=\"https:\/\/ucthpc.uct.ac.za\/wp-content\/uploads\/2015\/07\/newMem.png\" alt=\"New memory display\" border=\"0\" \/>\r\n\r\n&nbsp;","protected":false},"excerpt":{"rendered":"<p>We&#8217;re currently investigating a memory issue with some of the worker nodes.&nbsp; Memory is not being freed up after jobs complete.<\/p>\n<p>UPDATE &#8211; 4 July:<\/p>\n<p>Turns out it&#8217;s not a memory error.&nbsp; The problem is the way that net-snmp monitors and returns memory information.&nbsp; Unfortunately net-snmp clumps both real and cached memory together, so over time it looks as if memory available drops to zero.&nbsp; <a href=\"http:\/\/thwack.com\/forums\/48\/network-management\/9\/orion-network-performance-monitor\/18337\/linux-netsnmp-memory-usage-sh\/\">See this post for more info<\/a>.&nbsp; In order to fix this some jiggery-pokery may be required. <\/p>\n<p>UPDATE &#8211; 5 July: <\/p>\n<p>The issue is now resolved.&nbsp; By creating a custom snmp OID with a perl script which gets its information straight from \/etc\/proc we can get a far better idea of actual memory in use.&nbsp; This is displayed on the dashboard and also tracked in real time by our monitoring systems.<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/blogs.uct.ac.za\/gallery\/1253\/newMem.png\" border=\"0\" alt=\"New memory display\"><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[4,11],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Memory issues - UCT HPC<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Memory issues - UCT HPC\" \/>\n<meta property=\"og:description\" content=\"We&#039;re currently investigating a memory issue with some of the worker nodes.&nbsp; Memory is not being freed up after jobs complete.UPDATE - 4 July:Turns out it&#039;s not a memory error.&nbsp; The problem is the way that net-snmp monitors and returns memory information.&nbsp; Unfortunately net-snmp clumps both real and cached memory together, so over time it looks as if memory available drops to zero.&nbsp; See this post for more info.&nbsp; In order to fix this some jiggery-pokery may be required. UPDATE - 5 July: The issue is now resolved.&nbsp; By creating a custom snmp OID with a perl script which gets its information straight from \/etc\/proc we can get a far better idea of actual memory in use.&nbsp; This is displayed on the dashboard and also tracked in real time by our monitoring systems.&nbsp;\" \/>\n<meta property=\"og:url\" content=\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\" \/>\n<meta property=\"og:site_name\" content=\"UCT HPC\" \/>\n<meta property=\"article:published_time\" content=\"2011-07-02T14:33:38+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2022-09-26T18:02:18+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/ucthpc.uct.ac.za\/wp-content\/uploads\/2015\/07\/newMem.png\" \/>\n<meta name=\"author\" content=\"Andrew Lewis\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Andrew Lewis\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\"},\"author\":{\"name\":\"Andrew Lewis\",\"@id\":\"https:\/\/ucthpc.uct.ac.za\/#\/schema\/person\/c183ad1c0a1063124a72d63963ae9c7e\"},\"headline\":\"Memory issues\",\"datePublished\":\"2011-07-02T14:33:38+00:00\",\"dateModified\":\"2022-09-26T18:02:18+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\"},\"wordCount\":137,\"publisher\":{\"@id\":\"https:\/\/ucthpc.uct.ac.za\/#organization\"},\"articleSection\":[\"hpc\",\"operating system\"],\"inLanguage\":\"en-ZA\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\",\"url\":\"https:\/\/ucthpc.uct.ac.za\/index.php\/2011\/07\/02\/memory-issues\/\",\"name\":\"Memory issues - 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