7. Configuring and Managing VectorH : OS Settings : Virtual Address Space Allocation (Linux)
Share this page                  
Virtual Address Space Allocation (Linux)
For optimal performance, Vector by default allocates a large amount of virtual address space to be able to use it most efficiently when needed. In some circumstances, this amount can be larger than the amount of physical memory.
Some Linux distributions by default disallow reserving unlimited virtual address space. We recommend that you configure your system to allow unlimited allocation of virtual address space unless there are compelling reasons (unrelated to Vector) not to.
To check if your system allows unlimited allocation of virtual address space:
# cat /proc/sys/vm/overcommit_memory
should return 1.
# ulimit -v
should return unlimited.
To ensure the system does not limit allocation of virtual address space
Issue these commands after every system restart:
# echo 1 > /proc/sys/vm/overcommit_memory
# ulimit -v unlimited
To learn how to make this setting persistent, refer to your Linux documentation.
Alternatively, Vector can be configured to not reserve virtual address space by setting the [memory] max_overalloc (see  max_overalloc) configuration parameter to 0. This may limit the maximum performance your system can deliver.
Note:  If your system limits allocation of virtual address space by default, such allocation is automatically turned off in Vector during installation. If you reconfigure your system after Vector is installed to allow unlimited allocation of virtual address space, then you must also set the max_overalloc parameter correctly (to 2G by default).
To use the vwload command in parallel mode, /proc/sys/vm/overcommit_memory (see  Virtual Address Space Allocation (Linux)) must be set to 1 or [memory] max_overalloc (see  max_overalloc) must be 0.