Brian's Twiki documentation staging area

CMSSW I/O Activities

The following are notes from each CMSSW I/O project I've undertaken:

  • CmsIOWork - Patches to CMSSW. These improvements focus on getting the ROOT TTreeCache working.
  • CmsIOInstrumenting - Instrumenting the Linux kernel to provide a deeper understanding of how ROOT I/O interacts with the file system.
  • CmsIOWork2 - Next round of I/O improvements in CMSSW. These improvements focus on identifying all of the remaining "uncached" I/O usage, and making them going through the desired channels.
  • CmsIOFallback - Allow CMSSW to fallback to a fixed Xrootd URL if a file cannot be opened locally.
  • CmsIOHighLatency - Running CMSSW successfully on high latency links.
  • TestingFnalXrootd - Tests using the FNAL xrootd service.

The following is a list of changes I've been able to get into CMS software:

  • ROOT TTreecCache functioning (some items landed in 3.3; true functionality was in 3.6).
    • Squashing accompanying memory leak
  • ROOT TTreeCache on by default; 3.7
  • Fix broken caching on RAW files. 3.8 and 3.9
  • Fallback protocols in CMSSW. Upcoming (3.9?)
  • Xrootd stagein calls. Upcoming (3.9?)
  • Removal of non-Event TTrees. Important for high-latency links. Upcoming (3.9?)
I do not claim full ownership of all these items, as a few were implemented (or heavily improved) by others.

CMS Data Access Activities

CMS Singularity Support


FirstName Brian
LastName Bockelman



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This topic: Main > TWikiUsers > BrianBockelman
Topic revision: r18 - 2017-05-31 - BrianBockelman
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