This module is designed to help benchmark CMSSW I/O performance.

The IOExerciser EDAnalyzer reads a fixed percentage of branches from a

file (percentages are done by the size of the branch) and, at a fixed interval,

will read out all the data in an event.

To emulate production work, set the percent read to 100%. To emulate analysis

jobs, set the percent read to around 30% and the trigger factor to 10-100

(there's a wide range of analysis behavior).

To emulate a traditionally problematic I/O job, set the percent read to 10% and

the trigger factor to 10-20.

The selection strategy determines how branches are selected - smallest first,

largest first, or round robin:

- 'smallestFirst' (default): Read branches in increasing order of size until limit is hit.

- 'largestFirst': Read branches in decreasing order of size until limit is hit.

- 'roundRobin': Read a small branch, then large branch. Repeat until size limit is hit.

Smallest-first will allow you to stay closest to the desired percent read.

Round robin is likely closer to user behavior.

Run "edmPluginHelp -p IOExerciser" for online help.

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Here's an example configuration:

import FWCore.ParameterSet.Config as cms

process = cms.Process("Demo")

process.load("FWCore.MessageService.MessageLogger_cfi")

process.MessageLogger.cerr.FwkReport.reportEvery = 100

# Uncomment the following lines for thorough debugging info

#process.MessageLogger.debugModules.append("IOExerciser")

#process.MessageLogger.cerr.threshold = 'INFO'

#process.MessageLogger.cerr.INFO.limit = 500

process.maxEvents = cms.untracked.PSet( input = cms.untracked.int32(-1) )

process.source = cms.Source("PoolSource",

# replace 'myfile.root' with the source file you want to use

fileNames = cms.untracked.vstring(

'/store/mc/HC/GenericTTbar/GEN-SIM-RECO/CMSSW_5_3_1_START53_V5-v1/0010/A2B8D47D-BCAD-E111-B16A-BCAEC53296FB.root'

)

)

process.out = cms.OutputModule('IOExerciser',

percentBranches = cms.untracked.uint32(30),

triggerFactor = cms.untracked.uint32(20),

)

process.outpath = cms.EndPath(process.out)