11.3. Configuring HugeTLB at boot time

Procedure

1. Create a new file called hugetlb-gigantic-pages.service in the /usr/lib/systemd/system/ directory and add the following content:

   [Unit]
   Description=HugeTLB Gigantic Pages Reservation
   DefaultDependencies=no
   Before=dev-hugepages.mount
   ConditionPathExists=/sys/devices/system/node
   ConditionKernelCommandLine=hugepagesz=1G
   
   [Service]
   Type=oneshot
   RemainAfterExit=yes
   ExecStart=/usr/lib/systemd/hugetlb-reserve-pages.sh
   
   [Install]
   WantedBy=sysinit.target

2. Create a new file called hugetlb-reserve-pages.sh in the /usr/lib/systemd/ directory and add the following content:

   #!/bin/sh
   
   nodes_path=/sys/devices/system/node/
   if [ ! -d $nodes_path ]; then
       echo "ERROR: $nodes_path does not exist"
       exit 1
   fi
   
   reserve_pages()
   {
       echo $1 > $nodes_path/$2/hugepages/hugepages-1048576kB/nr_hugepages
   }
   
   reserve_pages <number_of_pages> <node>

   Replace <number_of_pages> with the number of 1GB pages you want to reserve, and <node> with the node name on which to reserve these pages. For example, to reserve two 1 GB pages on node0 and one 1GB page on node1, replace <number_of_pages> with 2 for node0 and 1 for node1.

3. Create an executable script:

   # chmod +x /usr/lib/systemd/hugetlb-reserve-pages.sh

4. Enable early boot reservation:

   # systemctl enable hugetlb-gigantic-pages.service

   注意
   • You can try reserving more 1 GB pages at runtime by writing to the nr_hugepages attribute at any time. However, to prevent failures due to memory fragmentation, reserve 1 GB pages early during the boot process.
   • Reserving static huge pages can effectively reduce the amount of memory available to the system, and prevent it from using its full memory capacity. Although a properly sized pool of reserved huge pages can be beneficial to applications that use it, an oversized or unused pool of reserved huge pages will eventually be detrimental to the overall system performance. When setting a reserved huge page pool, ensure that the system can properly use its full memory capacity.