Difference: CmsIOInstrumenting (1 vs. 2)

Revision 22010-03-22 - BrianBockelman

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META TOPICPARENT name="BrianBockelmanSandbox"

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:
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 BlockTrace, a set of scripts to record and visualize Linux kernel I/O.
  1. Using BlockTrace and SystemTap on your system. How to run BlockTrace on your systems in order to repeat the measurements I have made yourself.
  2. BlockTrace graphs. How to understand and read the BlockTrace graphs I will be showing.
Added:
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>
  1. User-level SystemTap tracing. Correlating between user-level events and kernel-level events.
  Findings for CMSSW
  1. CMSSW with readHint=application-only. This turns on TTreeCache, but does I/O in synchronous mode.

Revision 12010-03-16 - BrianBockelman

Line: 1 to 1
Added:
>
>
META TOPICPARENT name="BrianBockelmanSandbox"

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.
  2. Identify potential performance bottlenecks.
  3. Experiment with potential solutions.

Pages in this guide

BlockTrace, a set of scripts to record and visualize Linux kernel I/O.

  1. Using BlockTrace and SystemTap on your system. How to run BlockTrace on your systems in order to repeat the measurements I have made yourself.
  2. BlockTrace graphs. How to understand and read the BlockTrace graphs I will be showing.

Findings for CMSSW

  1. CMSSW with readHint=application-only. This turns on TTreeCache, but does I/O in synchronous mode.
  2. CMSSW with readHint=storage-only. This turns on TTreeCache with I/O in asynchronous mode.

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