and values approaching the depth of the BRQ queue (16) indicate a system under considerable stress.

•AVG BRQ Latency

This is the average number of cycles that a request resides in the BRQ. It is also useful for interpreting system loading. Large values (> 20 cycles) indicate that the processor is being delayed during bus request arbitration, probably due to excessive bus utilization by a priority agent (I/O).

•AVG IOQ Live Entries Per Cycle

The in-order queue (IOQ) monitors all outstanding bus transactions generated by any bus agent. Requests are loaded into the IOQ during the bus transaction request phase. Transactions are retired from the IOQ on receipt of a positive response status from the bus. This metric provides an estimate of the number of bus transactions that are live in the IOQ on a per-cycle basis. A high value for this metric would be indicative of high system bus utilization (many transactions in flight).

•AVG OOQ Live Entries Per Cycle

If a deferred response is received while a request is live in the IOQ, it is moved to the out-of-order queue (OOQ). When the response for the deferred transaction is received, the OOQ entry is moved to the end of the IOQ to complete the processing of the transaction. This metric provides the average number of requests that are live in the OOQ per cycle. High numbers of OOQ entries indicates excessive snoop response timing.

snoop Event Set

Available only on Itanium 9300 quad-core processor systems. The snoop event set provides data about snoop responses.

If you use this event set, the default is to make the measurements irrespective of CPU operating state (that is, user, system, or interrupt states). By default, the idle state is not included in the measurement. You can use command-line options to limit the scope of the measurement. Specifically, you can:

•Limit measurement to a specific privilege level: -m event_set[:alluserkernel]

•Include idle: --exclude-idle False

•Exclude the interruption state: --measure-on-interrupts off

•Only measure the interruption state: --measure-on-interrupts only

Metrics Available from this Measurement

The following metrics are available from this event set. These descriptions do not take into account any command-line options you might use.

The metrics are:

•Snoops Per Sec

Number of all snoops per second.

•Code

Percentage of snoops that are code snoops.

•Data

Percentage of snoops that are data snoops.

•Inv

Percentage snoops that are invalid snoops.

244 Event Set Descriptions for CPU Metrics