---+ Instrumenting CMSSW I/O This page discusses how to instrument CMSSW I/O at the Linux kernel in order to better understand how the application interacts with the block layer. The goals are: 1 Provide insights into how CMSSW (and hence ROOT) I/O's usage of various system calls results in disk activity. 1 Identify potential performance bottlenecks. 1 Experiment with potential solutions. ---+ Pages in this guide !BlockTrace, a set of scripts to record and visualize Linux kernel I/O. 1 [[Main.CmsIoBlockTrace][Using BlockTrace and !SystemTap on your system]]. How to run !BlockTrace on your systems in order to repeat the measurements I have made yourself. 1 [[Main.CmsIoBlockTraceOutput][BlockTrace graphs]]. How to understand and read the !BlockTrace graphs I will be showing. 1 [[Main.CmsIoSystemtap][User-level SystemTap tracing]]. Correlating between user-level events and kernel-level events. Findings for CMSSW 1 [[Main.CmsIoCmsswNocache][CMSSW with no cache]]. This is the out-of-the box behavior of CMSSW. 1 [[Main.CmsIoCmsswApp][CMSSW with readHint=application-only]]. This turns on !TTreeCache, but does I/O in synchronous mode. 1 [[Main.CmsIoCmsswStor][CMSSW with readHint=storage-only]]. This turns on !TTreeCache with I/O in asynchronous mode. 1 [[Main.CmsIoCmssw2Cache][CMSSW with the 2-cache scheme]]. This turns on the 2-cache scheme, as described by Main.CmsIOWork2.
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2010-03-16 - 16:46
BrianBockelman
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Topic revision: r5 - 2010-05-13 - BrianBockelman
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