Thread Settings
[Extended Qos Support]

The properties of a thread of execution. More...

Classes
class	DDS::ThreadSettings_t
	The properties of a thread of execution. More...
Enumerations
enum	DDS::ThreadSettingsKind {   DDS::THREAD_SETTINGS_FLOATING_POINT,   DDS::THREAD_SETTINGS_STDIO,   DDS::THREAD_SETTINGS_REALTIME_PRIORITY,   DDS::THREAD_SETTINGS_PRIORITY_ENFORCE ,   DDS::THREAD_SETTINGS_KIND_MASK_DEFAULT }
	A collection of flags used to configure threads of execution. More...
enum	DDS::ThreadSettingsCpuRotationKind {   DDS::THREAD_SETTINGS_CPU_NO_ROTATION,   DDS::THREAD_SETTINGS_CPU_RR_ROTATION }
	Determines how DDS::ThreadSettings_t::cpu_list affects processor affinity for thread-related QoS policies that apply to multiple threads. More...

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Detailed Description

The properties of a thread of execution.

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Enumeration Type Documentation

enum DDS::ThreadSettingsKind

A collection of flags used to configure threads of execution.

Not all of these options may be relevant for all operating systems.

See also:

DDS::ThreadSettingsKindMask

Enumerator:

THREAD_SETTINGS_FLOATING_POINT	Code executed within the thread may perform floating point operations.
THREAD_SETTINGS_STDIO	Code executed within the thread may access standard I/O.
THREAD_SETTINGS_REALTIME_PRIORITY	The thread will be schedule on a real-time basis.
THREAD_SETTINGS_PRIORITY_ENFORCE	Strictly enforce this thread's priority.
THREAD_SETTINGS_KIND_MASK_DEFAULT	The mask of default thread options.

enum DDS::ThreadSettingsCpuRotationKind

Determines how DDS::ThreadSettings_t::cpu_list affects processor affinity for thread-related QoS policies that apply to multiple threads.

Controlling CPU Core Affinity for RTI Threads

Most thread-related QoS settings apply to a single thread (such as for the DDS::EventQosPolicy, DDS::DatabaseQosPolicy, and DDS::AsynchronousPublisherQosPolicy). However, the thread settings in the DDS::ReceiverPoolQosPolicy control every receive thread created. In this case, there are several schemes to map M threads to N processors; the rotation kind controls which scheme is used.

If DDS::ThreadSettings_t::cpu_list is empty, the rotation is irrelevant since no affinity adjustment will occur. Suppose instead that DDS::ThreadSettings_t::cpu_list = {0, 1} and that the middleware creates three receive threads: {A, B, C}. If DDS::ThreadSettings_t::cpu_rotation is DDS::ThreadSettingsCpuRotationKind::THREAD_SETTINGS_CPU_NO_ROTATION, threads A, B and C will have the same processor affinities (0-1), and the OS will control thread scheduling within this bound. It is common to denote CPU affinities as a bitmask, where set bits represent allowed processors to run on. This mask is printed in hex, so a CPU core affinity of 0-1 can be represented by the mask 0x3.

If DDS::ThreadSettings_t::cpu_rotation is DDS::ThreadSettingsCpuRotationKind::THREAD_SETTINGS_CPU_RR_ROTATION, each thread will be assigned in round-robin fashion to one of the processors in DDS::ThreadSettings_t::cpu_list; perhaps thread A to 0, B to 1, and C to 0. Note that the order in which internal middleware threads spawn is unspecified.

Not all of these options may be relevant for all operating systems.

Enumerator:

THREAD_SETTINGS_CPU_NO_ROTATION	Any thread controlled by this QoS can run on any listed processor, as determined by OS scheduling.
THREAD_SETTINGS_CPU_RR_ROTATION	Threads controlled by this QoS will be assigned one processor from the list in round-robin order.