<GCHeapAffinitizeMask> element

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Defines the affinity between GC heaps and individual processors.

<configuration>
  <runtime>
    <GCHeapAffinitizeMask>

Syntax

<GCHeapAffinitizeMask
   enabled="nnnn"/>

Attributes and elements

The following sections describe attributes, child elements, and parent elements.

Attributes

Attribute Description
enabled Required attribute.

Specifies the affinity between GC heaps and individual processors.

enabled attribute

Value Description
nnnn A decimal value that forms a bitmask defining the affinity between server GC heaps and individual processors.

Child elements

None.

Parent elements

Element Description
configuration The root element in every configuration file used by the common language runtime and .NET Framework applications.
runtime Contains information about assembly binding and garbage collection.

Remarks

By default, server GC threads are hard-affinitized with their respective CPU so that there is one GC heap, one server GC thread, and one background server GC thread for each processor. Starting with .NET Framework 4.6.2, you can use the GCHeapAffinitizeMask element to control the affinity between server GC heaps and processors when the number of heaps is limited by the GCHeapCount element.

GCHeapAffinitizeMask is typically used along with two other flags:

  • GCNoAffinitize, which controls whether server GC threads/heaps are affinitized with CPUs. The enabled attribute of the GCNoAffinitize element must be false (its default value) for the GCHeapAffinitizeMask setting to be used.

  • GCHeapCount, which limits the number of heaps used by the process for server GC. By default, there is one heap for each processor.

nnnn is a bit mask expressed as a decimal value. Bit 0 of byte 0 represents processor 0, bit 1 of byte 0 represents processor 1, and so on. For example:

<GCHeapAffinitizeMask enabled="1023"/>

A value of 1023 is 0x3FF or 0011 1111 1111b. The process uses 10 processors, from processor 0 through processor 9.

Example

The following example indicates that an application uses server GC with 10 heaps/threads. Since you don't want those heaps to overlap with heaps from other applications running on the system, use GCHeapAffinitizeMask to specify that the process should use CPUs 0 through 9.

<configuration>
   <runtime>
      <gcServer enabled="true"/>
      <GCHeapCount enabled="10"/>
      <GCHeapAffinitizeMask enabled="1023"/>
   </runtime>
</configuration>

See also