docs - add resgroup seg memory calculation to resgroup page
href="../ref_guide/config_params/guc-list.xml#gp_resource_group_cpu_limit"
type="section"/></codeph> server configuration parameter identifies the maximum
percentage of system CPU resources to allocate to resource groups on each Greenplum Database
- segment node. The remaining CPU resources are used for the OS kernel and the Greenplum
+ segment host. The remaining CPU resources are used for the OS kernel and the Greenplum
Database auxiliary daemon processes. The default
<codeph>gp_resource_group_cpu_limit</codeph> value is .9 (90%).</p>
<note>The default <codeph>gp_resource_group_cpu_limit</codeph> value may not leave sufficient
href="../ref_guide/config_params/guc-list.xml#gp_resource_group_memory_limit"
type="section"/></codeph> server configuration parameter identifies the maximum
percentage of system memory resources to allocate to resource groups on each Greenplum
- Database segment node. The default <codeph>gp_resource_group_memory_limit</codeph> value is
+ Database segment host. The default <codeph>gp_resource_group_memory_limit</codeph> value is
.7 (70%).</p>
<p>The memory resource available on a Greenplum Database node is further divided equally among
- each segment on the node. Each resource group reserves a percentage of the segment memory
+ each segment on the node.
+ When resource group-based resource management is active, the amount of memory allocated
+ to each segment on a segment host is the memory available to Greenplum Database multiplied by the
+ <codeph>gp_resource_group_memory_limit</codeph> server configuration parameter and
+ divided by the number of active primary segments on the host:</p>
+ <p><codeblock>
+rg_perseg_mem = ((RAM * (vm.overcommit_ratio / 100) + SWAP) * gp_resource_group_memory_limit) / num_active_primary_segments</codeblock></p>
+ <p>Each resource group reserves a percentage of the segment memory
for resource management. You identify this percentage via the <codeph>MEMORY_LIMIT</codeph>
value you specify when you create the resource group. The minimum
<codeph>MEMORY_LIMIT</codeph> percentage you can specify for a resource group is 1, the
