Logging events with timestamps

A method of logging events in a computer system by storing entries in a store, each of said entries comprising an n-bit timestamp field and a payload, the method comprising:

• determining a timestamp for an event which is to be logged, wherein the determined timestamp comprises N bits, where N>n;
• determining whether one or more of the N−n most significant bits of the determined timestamp are different to a corresponding one or more of the N−n most significant bits of a timestamp for a preceding event for which a preceding event entry is stored in the store;
• in response to determining that one or more of the N−n most significant bits of the determined timestamp are different to a corresponding one or more of the N−n most significant bits of a timestamp for a preceding event for which a preceding event entry is stored in the store, storing a timing entry in the store, said timing entry including a set of k bits of the determined timestamp, said k bits being more significant bits of the determined timestamp than the n least significant bits of the determined timestamp;
• and
• storing an event entry for the event in the store, wherein the n least significant bits of the determined timestamp are included in the timestamp field of the event entry for the event.

A method of retrieving, from a store configured to store entries, information relating to a particular event in a computer system, each of said entries comprising an n-bit timestamp field and a payload, and wherein the particular event is associated with a timestamp comprising N bits, where N>n, the method comprising:

• reading a particular event entry for the particular event from the store, wherein the n least significant bits of the timestamp are included in the timestamp field of the particular event entry;
• identifying a timing entry preceding the particular event entry in the store, wherein the identified timing entry includes a set of k bits of the timestamp for the particular event, said k bits being more significant bits of the timestamp than the n least significant bits of the timestamp;
• concatenating the k bits of the timestamp from the identified timing entry with the n bits of the timestamp from the timestamp field of the particular event entry, for use in constructing the timestamp for the particular event;
• and
• outputting the constructed timestamp for the particular event.

A non-transitory computer readable storage medium having stored thereon a computer readable description of an integrated circuit that, when processed in an integrated circuit manufacturing system, causes the integrated circuit manufacturing system to manufacture a logging unit, the logging unit being for logging events in a computer system by causing entries to be stored in a store, wherein each of said entries comprises an n-bit timestamp field and a payload, the logging unit comprising control logic configured to:

• determine a timestamp for an event which is to be logged, wherein the determined timestamp comprises N bits, where N>n;
• determine whether one or more of the N−n most significant bits of the determined timestamp are different to a corresponding one or more of the N−n most significant bits of a timestamp for a preceding event for which a preceding event entry is stored in the store;
• cause a timing entry which includes a set of k bits of the determined timestamp to be stored in the store in response to determining that one or more of the N most significant bits of the determined timestamp are different to a corresponding one or more of the N−n most significant bits of a timestamp for a preceding event for which a preceding event entry is stored in the store, said k bits being more significant bits of the determined timestamp than the n least significant bits of the determined timestamp;
• and
• cause an event entry for the event to be stored in the store, wherein the n least significant bits of the determined timestamp are included in the timestamp field of the event entry for the event.