1.0UCT HPChttps://ucthpc.uct.ac.zaAndrew Lewishttps://ucthpc.uct.ac.za/index.php/author/andrew-lewis/rich600338<blockquote class="wp-embedded-content" data-secret="wFZiwRMFJr"><a href="https://ucthpc.uct.ac.za/index.php/2015/06/26/slurm-and-memory-management/">SLURM and memory management</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="https://ucthpc.uct.ac.za/index.php/2015/06/26/slurm-and-memory-management/embed/#?secret=wFZiwRMFJr" width="600" height="338" title="“SLURM and memory management” — UCT HPC" data-secret="wFZiwRMFJr" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script type="text/javascript"> /*! This file is auto-generated */ !function(c,d){"use strict";var e=!1,o=!1;if(d.querySelector)if(c.addEventListener)e=!0;if(c.wp=c.wp||{},c.wp.receiveEmbedMessage);else if(c.wp.receiveEmbedMessage=function(e){var t=e.data;if(!t);else if(!(t.secret||t.message||t.value));else if(/[^a-zA-Z0-9]/.test(t.secret));else{for(var r,s,a,i=d.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),n=d.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),o=new RegExp("^https?:$","i"),l=0;l<n.length;l++)n[l].style.display="none";for(l=0;l<i.length;l++)if(r=i[l],e.source!==r.contentWindow);else{if(r.removeAttribute("style"),"height"===t.message){if(1e3<(s=parseInt(t.value,10)))s=1e3;else if(~~s<200)s=200;r.height=s}if("link"===t.message)if(s=d.createElement("a"),a=d.createElement("a"),s.href=r.getAttribute("src"),a.href=t.value,!o.test(a.protocol));else if(a.host===s.host)if(d.activeElement===r)c.top.location.href=t.value}}},e)c.addEventListener("message",c.wp.receiveEmbedMessage,!1),d.addEventListener("DOMContentLoaded",t,!1),c.addEventListener("load",t,!1);function t(){if(o);else{o=!0;for(var e,t,r,s=-1!==navigator.appVersion.indexOf("MSIE 10"),a=!!navigator.userAgent.match(/Trident.*rv:11\./),i=d.querySelectorAll("iframe.wp-embedded-content"),n=0;n<i.length;n++){if(!(r=(t=i[n]).getAttribute("data-secret")))r=Math.random().toString(36).substr(2,10),t.src+="#?secret="+r,t.setAttribute("data-secret",r);if(s||a)(e=t.cloneNode(!0)).removeAttribute("security"),t.parentNode.replaceChild(e,t);t.contentWindow.postMessage({message:"ready",secret:r},"*")}}}}(window,document); </script> SLURM allows a DefMemPerCPU and a MaxMemPerCPU to be set. If a user does not set a memory limit the default will be used. This is normally set to MaxMem/NumCores. As memory is a consumable resource (SelectTypeParameters=CR_Core_Memory) MaxMemPerCPU serves not only to protect the node's memory but will also automatically increase a job's core count on submission where possible. Below are 5 similar jobs submited by a user, each one requiring more memory. The nodes all have 2GB of RAM per core. The initial --ntasks (cores) of each job is set to 1. However as MaxMemPerCPU is set to 2GB the number of cores is increased by the scheduler to a of multiple of each 2GB or RAM requested.#  JOBID                         NAME  USER CPUS      NODELIST      ----------------------------------------------------------------------------1   2043      Mem_Test_500M   andy       1    srvcnthpc408    2   2044    Mem_Test_2000M   andy       1    srvcnthpc408     3   2045    Mem_Test_5000M   andy       3    srvcnthpc406     4   2046    Mem_Test_8000M   andy       4    srvcnthpc406     5   2047  Mem_Test_10000M   andy       5    srvcnthpc407