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Enable Transparent Huge Pages

The Fastcapa probe performs its own memory management by leveraging Transparent Huge Pages (THP). In Linux, you can use the Transparent Huge Pages to enable either dynamically or automatically upon startup. Hortonworks recommends that these be allocated on boot to increase the chance that a larger, physically contiguous chunk of memory allocated.

For better performance, allocate 1 GB THPs if supported by your CPU.
  1. Ensure that your CPU supports 1 GB THPs. A CPU flag pdpe1gb indicates whether or not the CPU supports 1 GB THPs.
    grep --color=always pdpe1gb /proc/cpuinfo | uniq
  2. Edit /etc/default/grub to add the following book parameters at the line starting with GRUB_CMDLINE_LINUX:
    GRUB_CMDLINE_LINUX=... default_hugepagesz=1G hugepagesz=1G hugepages=16
  3. Rebuild the Grub configuration then reboot. The location of the Grub configuration file will differ across Linux distributions.
    cp /etc/grub2-efi.cfg /etc/grub2-efi.cfg.orig
    /sbin/grub2-mkconfig -o /etc/grub2-efi.cfg
  4. After the host reboots, ensure that the THPs were successfully allocated:
    $ grep HugePage /proc/meminfo
    AnonHugePages:    933888 kB
    HugePages_Total:      16
    HugePages_Free:        0
    HugePages_Rsvd:        0
    HugePages_Surp:        0
    The total number of huge pages should be distributed fairly evenly across each non-uniform memory access (NUMA) node. In the following example, a total of 16 requested THPs are distributed as 8 to each of 2 NUMA nodes:
    $ cat /sys/devices/system/node/node*/hugepages/hugepages-1048576kB/nr_hugepages
  5. After the THPs are reserved, mount them to make them available to the probe:
    cp /etc/fstab /etc/fstab.orig
    mkdir -p /mnt/huge_1GB
    echo "nodev /mnt/huge_1GB hugetlbfs pagesize=1GB 0 0" >> /etc/fstab
    mount -fav