Commonly Used Metrics for Performance Analysis - Power.org

More documents

Recommendations

Info

Metrics for Performance Analysis5 Linux Tools for Collecting PMC DataThe Linux tools oprofile and perf can collect performance event counts. They provide similar information(event counts per function). The two tools’ command lines also have similar syntax.5.1 perfperf is a standard Linux profiling tool with direct support in the kernel. It is not usually built/installed by default,but for recent kernels (2.6.34+) it can be built from the kernel source tree directly at /usr/src/linux-/tools/perf/. Details and scripts for managing perf data collection are found at this developerworkswebsite.Note: perf uses raw event codes to collect event data through the perf command line. The raw event code isthe number of the PMC to use (PMC1-PMC4 or “0” for any counter) concatenated with the PMC event codegiven in the “Comprehensive PMU Event Reference: POWER7” document. For convenience, the“run_example.py” script described on the website allows the user to supply event names (mnemonics)instead of raw event codes.The perf wiki is another good source of information.5.2 oprofileoprofile is a system-wide profiler for Linux, capable of profiling all running code at low overhead. It consistsof a kernel driver and a daemon for collecting sample data, and several post-processing tools for turning datainto information. oprofile leverages the hardware performance counters of the CPU to enable profiling of awide variety of interesting statistics, which can also be used for basic time-spent profiling.More details on using oprofile are available in the Performance Guide For HPC Applications On IBM Power755 System. Though its syntax is different, its usage is analogous to that of perf, as described in section 5.1,above.The official website for oprofile is here. Specifying events for oprofile is discussed here.Copyright ©2011 IBM Corporation Page 16 of 52
Metrics for Performance Analysis6 CPI StackThis chapter lists and describes the events, metrics and groups needed for the CPI stack analysis.6.1 Descriptions of EventsThere are 26 events, distributed across 11 event groups, needed to complete the POWER7 CPI stack. Theseinclude 2 architected events counting non-idle completed instructions and non-idle cycles.This section provides more details on each event and how it is triggered. Since instruction groups have tocomplete in order, a group can’t complete until all instructions in the group finish. So a stall is all of the cyclesbetween two groups completing. The general rule is that if a completion stall has occurred, the last instructionto finish (regardless of how many instructions were stalled) is charged with the entire stall. The practicalconsequence of this is that eliminating a stall (e.g. an ERAT miss) from an execution pipeline may reveal anew stall (e.g. a data cache miss).PM_1PLUS_PPC_CMPL1 or more ppc instructions finishedA group containing at least one PowerPC instruction completed. For microcoded instructions that spanmultiple groups, this will only occur once.PM_CMPLU_STALLNo groups completed, GCT not emptyThose cycles where a thread was not completing any groups, but the group completion table had entries forthat thread.PM_CMPLU_STALL_BRUCompletion stall due to BRU.Following a completion stall (any period when no groups completed, while group completion table was notempty for that thread) the last instruction to finish before completion resumes was from the Branch Unit.PM_CMPLU_STALL_DCACHE_MISS Completion stall caused by D cache missFollowing a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes suffered a Data Cache Miss. AData Cache Miss has higher priority than any other Load/Store delay, so if an instruction encounters multipledelays, only the Data Cache Miss will be reported and the entire delay period will be charged to the DataCache Miss.PM_CMPLU_STALL_DFU Completion stall caused by Decimal Floating Point UnitFollowing a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes was from the Decimal FloatingPoint Unit.PM_CMPLU_STALL_DIV Completion stall caused by DIV instructionFollowing a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes was a fixed point divideinstruction.PM_CMPLU_STALL_ERAT_MISS Completion stall caused by ERAT missFollowing a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes suffered an ERAT miss.PM_CMPLU_STALL_FXUCompletion stall caused by FXU instructionFollowing a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes was from the Fixed Point Unit.PM_CMPLU_STALL_IFUCompletion stall due to IFU.Following a completion stall (any period when no groups completed and the group completion table was notempty for that thread) the last instruction to finish before completion resumes was from the Instruction FetchCopyright ©2011 IBM Corporation Page 17 of 52
Page 4 and 5: Metrics for Performance AnalysisTab
Page 6 and 7: Metrics for Performance Analysis2 T
Page 8 and 9: Metrics for Performance Analysis3 T
Page 10 and 11: Metrics for Performance Analysistha
Page 12 and 13: Metrics for Performance Analysisact
Page 14 and 15: Metrics for Performance Analysisexp
Page 18 and 19: Metrics for Performance AnalysisUni
Page 20 and 21: Metrics for Performance AnalysisIFU
Page 22 and 23: Metrics for Performance AnalysisTab
Page 24 and 25: Metrics for Performance Analysis7 M
Page 26 and 27: Metrics for Performance Analysis8 L
Page 28 and 29: Metrics for Performance Analysis9 B
Page 30 and 31: Metrics for Performance Analysis9.3
Page 32 and 33: Metrics for Performance Analysisdem
Page 34 and 35: Metrics for Performance Analysispm_
Page 36 and 37: Metrics for Performance Analysiscol
Page 38 and 39: Metrics for Performance AnalysisFor
Page 40 and 41: Metrics for Performance Analysis13
Page 42 and 43: Metrics for Performance AnalysisINS
Page 48 and 49: Metrics for Performance AnalysisApp
Page 50 and 51: Metrics for Performance AnalysisThi
Page 52: Metrics for Performance AnalysisTel

Commonly Used Metrics for Performance Analysis - Power.org

Create successful ePaper yourself

Delete template?

Save as template?