<p>Here&#8217;s a simple thing that I ran across. I have a vendor that recommended that I set the Maximum memory in my LPARs to the system maximum.  That way you never have to reboot to increase the maximum memory in that LPAR. I found out later that setting your LPARs memory to the system maximum makes the hypervisor allocate more memory for overhead.</p>
<p>This is a very old configuration issue, but I just ran across the actual numbers. When the LPAR is activated, the hypervisor allocates 1/64th the LPAR maximum for page frame tables. This is a memory structure that the hypervisor uses to track the memory pages used by the LPAR. So, lets say you have a 128GB managed system with LPARs that only really need 16GB of RAM, but the LPAR&#8217;s maximum memory is set to 128GB.  By the time you&#8217;ve activated your 7th LPAR your using 2GB per LPAR, or 14GB of RAM, just for the hypervisor memory page frame tables.</p>
{"id":666,"date":"2011-02-27T19:14:53","date_gmt":"2011-02-27T23:14:53","guid":{"rendered":"http:\/\/patrickv.info\/wordpress\/?p=666"},"modified":"2011-02-27T19:14:53","modified_gmt":"2011-02-27T23:14:53","slug":"lpar-memory-overhead","status":"publish","type":"post","link":"https:\/\/rootuser.ninja\/index.php\/2011\/02\/27\/lpar-memory-overhead\/","title":{"rendered":"LPAR Memory Overhead"},"content":{"rendered":"<p>Here&#8217;s a simple thing that I ran across. I have a vendor that recommended that I set the Maximum memory in my LPARs to the system maximum.  That way you never have to reboot to increase the maximum memory in that LPAR. I found out later that setting your LPARs memory to the system maximum makes the hypervisor allocate more memory for overhead.<\/p>\n<p>This is a very old configuration issue, but I just ran across the actual numbers. When the LPAR is activated, the hypervisor allocates 1\/64th the LPAR maximum for page frame tables. This is a memory structure that the hypervisor uses to track the memory pages used by the LPAR. So, lets say you have a 128GB managed system with LPARs that only really need 16GB of RAM, but the LPAR&#8217;s maximum memory is set to 128GB.  By the time you&#8217;ve activated your 7th LPAR your using 2GB per LPAR, or 14GB of RAM, just for the hypervisor memory page frame tables.<\/p>\n","protected":false},"excerpt":{"rendered":null,"protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,1],"tags":[],"class_list":["post-666","post","type-post","status-publish","format-standard","hentry","category-aix-notes","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/posts\/666","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/comments?post=666"}],"version-history":[{"count":0,"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/posts\/666\/revisions"}],"wp:attachment":[{"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/media?parent=666"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/categories?post=666"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rootuser.ninja\/index.php\/wp-json\/wp\/v2\/tags?post=666"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}