13.4.1 Reducing the usage of shared memory to which HugePages is applied
When HugePages is applied to the HADB server's shared memory, an unnecessarily large amount of memory might be allocated. As a result, performance of the Linux kernel, for example, might decline.
Whenever HugePages is applied to the HADB server's shared memory, check whether the allocated amount of memory is appropriate. The following procedure explains how to perform tuning:
Procedure
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Check the maximum usage of all memory.
Check the following item in the HADB server statistical information that is output when the adbstat command is executed:
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Total_memory_max_size (maximum usage of all memory)
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Check the kernel parameter.
Check the value specified for the vm.nr_hugepages kernel parameter that was set in the operating system of the machine where the HADB server was installed.
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Check whether the allocated amount of memory is appropriate.
If the value specified for vm.nr_hugepages (step 2) is greater than the value output to Total_memory_max_size (step 1), an unnecessarily large amount of memory has been allocated. Reduce the value specified for vm.nr_hugepages to match the value output to Total_memory_max_size.
- Important
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After you terminate the HADB server by executing the adbstop command, change the value specified for vm.nr_hugepages.
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Restart the OS.
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Change the server definition.
If you changed the value specified for vm.nr_hugepages in step 3, change also the value of the adb_sys_memory_limit operand in the server definition.
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Start the HADB server.
Execute the adbstart command to start the HADB server.
- Note
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For details about the adb_sys_memory_limit operand in the server definition, see the adb_sys_memory_limit operand in 7.2.2 Operands related to performance (set format).