Configuring HugePages

Configure Linux HugePages for DPME DRAM caching by calculating how many HugePages your system needs and setting the vm.nr_hugepages kernel parameter to the value.

About this task

DPME uses 2MB translation lookaside buffer (TLB) pages to cache data between PMEM and DRAM.

To use HugePages, you must allocate a HugePages pool on the server.

Procedure

  1. Calculate the number of HugePages needed on your system. Since Memory Machine uses 2 MB HugePages, a system requires 500 HugePages for every one GB of DRAM to be used for TLB.
    If you plan to use all of the server's memory to run Memory Machine-managed applications, create enough HugePages for 90% of the server's DRAM. (The OS requires the remaining 10% of DRAM to run.) So for example if the system has 64 GB of DRAM, the system requires HugePages for 64 * 0.9 = 57.6 GB, so allocate 57.6 * 500 = 28800 HugePages.
  2. Use the sysctl command to set the vm.nr_hugepages kernel variable to the calculated number of HugePages. For example: 
    # sysctl -w vm.nr_hugepages=28800
  3. To automatically set the HugePages at bootup (to avoid having to set HugePages after every restart), add the following line to the appropriate system control file (for example, /etc/sysctl.conf) for your server. 
    vm.nr_hugepages=hugepage_count
    where hugepage_count is the number of HugePages that you calculated in step 1.