Tracing synchronization activity of a processing unit

A method for tracing synchronisation activity for a processor of a processing unit, the method comprising:

• exchanging a plurality of sync messages between a sync controller hardware unit and the processor so as to co-ordinate a plurality of barrier synchronisations, each of the barrier synchronisations separating a compute phase of the processor from an exchange phase for the processor;
• receiving at sync trace circuitry, a first sync message of the plurality of sync messages;
• and
• in response to the first sync message, providing sync trace information for output from a device comprising the sync trace circuitry, the sync trace information comprising timing information associated with the first sync message,
• wherein a plurality of dedicated wires are used for transmitting different types of sync message between the processing unit and the sync controller hardware unit,
• wherein exchanging the plurality of sync messages comprises at least one of:
• asserting signals on at least one of the dedicated wires;
• and
• detecting assertion of signals by circuitry of the sync controller hardware unit on a further at least one of the dedicated wires,
• wherein the sync trace circuitry comprises a plurality of connections to different ones of the dedicated wires, and
• wherein the method further comprises:
• for each of the plurality of sync messages, providing the respective sync trace information in dependence upon which of the dedicated wires an assertion of a signal corresponding to the respective sync message was detected.

A non-transitory computer readable medium storing computer readable instructions, which when executed by at least one processor, causes a method to be carried out, the method comprising:

• receiving a plurality of sync messages from a sync controller hardware unit, wherein each of the sync messages is a message to co-ordinate a barrier synchronisation separating a compute phase of at least part of a processing unit from an exchange phase of the at least part of the processing unit;
• and
• in response to a first sync message of the plurality of sync messages, providing sync trace information for output from a device comprising the processing unit, the sync trace information comprising timing information associated with the first sync message,
• wherein the sync trace information further comprises identification of a sync group for one of the barrier synchronisations that is associated with the first sync message,
• wherein the sync controller hardware unit comprises a plurality of interfaces, each of which is associated with a different sync group, and
• wherein the method further comprises:
• determining, for the first sync message, the identification of the sync group in dependence upon which of the plurality of interfaces the first sync message is issued or received on.