Add a method to EventMsgBuilder to precompute the message header size [12.4.x]

[fwyzard]

PR description:

Add a method to EventMsgBuilder to precompute the message header size, instead of relying on a small fixed-size buffer.

PR validation:

Validated running ./EventFilter/Utilities/test/RunBUFU.sh with larger than usual number of HLT paths.

if this PR is a backport please specify the original PR and why you need to backport that PR:

Backport of #37959 (using the same branch).

[fwyzard]

backport #37959

[fwyzard]

please test

[cmsbuild]

A new Pull Request was created by @fwyzard (Andrea Bocci) for CMSSW_12_4_X.

It involves the following packages:

• IOPool/Streamer (core)

@makortel, @smuzaffar, @Dr15Jones can you please review it and eventually sign? Thanks.
@makortel, @wddgit this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

• Backported from Add a method to EventMsgBuilder to precompute the message header size #37959

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-ac2b4a/24768/summary.html
COMMIT: 1412758
CMSSW: CMSSW_12_4_X_2022-05-16-2300/slc7_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/37967/24768/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

@slava77 comparisons for the following workflows were not done due to missing matrix map:

• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-ac2b4a/11634.301_TTbar_14TeV+2021_Run3FS+TTbar_14TeV_TuneCP5_GenSim+HARVESTNano

Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 50
• DQMHistoTests: Total histograms compared: 3741432
• DQMHistoTests: Total failures: 7
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 3741402
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: -0.004 KiB( 49 files compared)
• DQMHistoSizes: changed ( 312.0 ): -0.004 KiB MessageLogger/Warnings
• Checked 208 log files, 45 edm output root files, 50 DQM output files
• TriggerResults: no differences found

[makortel]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_12_4_X IBs (tests are also fine) and once validation in the development release cycle CMSSW_12_5_X is complete. This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[perrotta]

+1