HP UX Caliper Software Dcache Measurement Report Description, How cycles Metrics Are Obtained

Table 20 Information in cycles Measurement Reports (continued)

Column	Description
Function	Routine from your application.
File	Source file associated with a function.
Cycles Per Bundle	The average number of cycles elapsed to retire the bundle. If there are no stalls, it should take
	exactly one cycle to retire a bundle. If the Cycles Per Bundle information is more than 1, this
	means that many additional cycles of stall were seen on that bundle.
	If the Cycles per Bundle information is prefixed with an asterisk (*), that means that instructions
	from that bundle are split issued.
Line	The column contains one of these:
Slot	• A source-code line number for rows showing statements
Col,Offset
	• An instruction slot number for rows showing instructions not on a bundle boundary
	• A source-code column number followed by an offset from the beginning address of a function
	for rows showing instructions on a bundle boundary
	Column and line numbers are preceded by “~” when they are approximate due to optimization.
>Statement	The column contains either a source statement preceded by “>” or a disassembled instruction.
Instruction	Statements that are out of order due to optimization are preceded by “*>”.

How cycles Metrics Are Obtained

HP Caliper obtains cycles metrics using the execution trace buffer (ETB) of the performance monitoring unit (PMU). The ETB is configured to capture IPs of retired instructions. When a bundle is retired, the IP address and the number of elapsed cycles to retire the bundle are recorded in the ETB. The dual-core Itanium 2 and Itanium 9300 quad-core processor ETB is a circular buffer and can contain up to 16 entries.

HP Caliper takes samples by using the overflow of one of the PMU's event counters as a sampling trigger. Samples are taken every Nth PMU event, where both N and the sampling event are defined in the cycles measurement configuration file in the HP Caliper home directory in the config subdirectory. You can override the value in the measurement configuration file by using the -soption.

The list of processor metrics you can use for the sampling event are available from the file itanium2_cpu_counters.txt, located in the HP Caliper home directory in the doc/text subdirectory.

The ETB collected at each sampling point can contain up to 16 IPs. By default, cycles will pick the youngest IP sample from the ETB. However, all the 16 IP entries are processed to collect the elapsed cycles (Cycles Per Bundle) information. If two consecutive IP entries have the same bundle address, it is treated as a split issue (that is, it required multiple cycles to issue that bundle).

You can use the --etb-freeze-delayand --etb-walkback-cyclesoptions to correlate the performance monitoring events to IP values. The option --etb-freeze-delaychanges the way in which the ETB collects the IP samples. The option --etb-walkback-cycleschanges the way in which HP Caliper picks the IP sample from the 16 IP entries in an ETB sample.

dcache Measurement Report Description

With the dcache measurement, produced by the dcache measurement configuration file, HP Caliper measures and reports on data cache metrics. This measurement is similar to the icache measurement.

The report shows two levels of information:

•Exact counts of data cache metrics summed across the entire run of an application

•Sampled data cache metrics that are associated with particular locations in the application

186 Descriptions of Measurement Reports