◦%Indirect Branch

◦This metric provides the percentage of Indirect branches among all branches.

◦%Return Branch

This metric provides the percentage of Return branches among all branches.

•IPREL Path Statistics

This metric provides path distribution and mispredict rate for both paths of a non-call IPREL branch. Unconditional IPREL branches are included, so there is a slight bias toward the taken path. There is also an untaken bias that is an artifact of the Itanium 2's branch semantics defined by the PMU. In the Itanium 2, predicated off branches are considered retired untaken branches. Thus, the untaken category will be biased by predicated off branches. For most commercial applications, the untaken path will dominate if PBO has been successfully applied.

◦%Taken

Percentage of taken non-call IPREL branches.

◦%Taken Mispredicted (%mpb)

Percentage of mispredicted taken non-call IPREL branches.

◦%Untaken

Percentage of non-taken non-call IPREL branches.

◦%Untaken Mispredicted (%mpb)

Percentage of mispredicted non-taken non-call IPREL branches.

brpred Event Set

The brpred event set provides information useful in assessing the effectiveness of branch prediction for the three major classes of branches: IPREL, Indirect, and Return.

The Itanium 2's branch semantics considers predicated off branches as retired untaken branches. So the branch statistics include the impact of predicated off branches that were predicated to be a taken branch. For each branch class (IPREL, Indirect, and Return), the frequency weight, percentage of correct, wrong path, and wrong target prediction outcomes is provided. The weight is the fractional part of each prediction outcome for each branch category that applies to the overall branch prediction statistics.

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.

220 Event Set Descriptions for CPU Metrics