Streamer input source prefetching (12_5_X)

[smorovic]

PR description:

Adds a preallocated buffer intended to avoid many small reads when reading streamer files. This is aimed at improving EOS reading performance (see #38997).
A pointer to the big buffer is passed if possible for reading header and even payloads (contiguous), otherwise data is copied to the intermediate header or event buffer.

New parameter enables and configures size of the large buffer in MBytes (0 to disable), for example:

process.source = cms.Source("NewEventStreamFileReader",
    prefetchMBytes = cms.untracked.uint32(100),

PR validation:

A new unit test in IOPool/Streamer specifically checks behavior with this parameter (1 MB with small generated events). A file larger than the buffer was created to test behavior at the buffer boundary.
Internally, source checks adler32 checksum of both the header and event payload (compared to a header field), so corruption of payloads would be caught by unit tests.

Streamer source in CalibCalorimetry/EcalLaserSorting uses this code and has a respective unit test in that location.
Similarly, DQM streamer input source is tested as part of DAQ I/O chain in EventFilter/Utilities unit test.

[cmsbuild]

-code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31600

• This PR adds an extra 20KB to repository

Code check has found code style and quality issues which could be resolved by applying following patch(s)

• code-format:
  https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31600/code-format.patch
  e.g. curl -k https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31600/code-format.patch | patch -p1
  You can also run scram build code-format to apply code format directly

[smorovic]

12_4_X backport branch (PR will be created after this is reviewed):
https://github.com/smorovic/cmssw/tree/12_4_X-streamer-prebuffering

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31601

• This PR adds an extra 20KB to repository

[cmsbuild]

A new Pull Request was created by @smorovic (Srecko Morovic) for master.

It involves the following packages:

• IOPool/Streamer (core)

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

cms-bot commands are listed here

[smorovic]

@cmsbuild please test

[smorovic]

abort test

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31604

• This PR adds an extra 20KB to repository

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39088/31669

• This PR adds an extra 16KB to repository

[cmsbuild]

Pull request #39088 was updated. @cmsbuild, @smuzaffar, @Dr15Jones, @makortel can you please check and sign again.

[smorovic]

Apparently the Event Header
https://github.com/cms-sw/cmssw/blob/master/IOPool/Streamer/interface/EventMessage.h#L61
and also this header which is part of it:
https://github.com/cms-sw/cmssw/blob/master/IOPool/Streamer/interface/MsgHeader.h#L6
consist fully of of char and char arrays which are defined here:
https://github.com/cms-sw/cmssw/blob/master/IOPool/Streamer/interface/MsgTools.h#L15

EventMsgView uses char* pointer to traverse through the message:
https://github.com/cms-sw/cmssw/blob/master/IOPool/Streamer/src/EventMessage.cc#L4
and builds higher-order variables from individual bytes (like with the convert32 function).

Conclusion is that alignment is not an issue. So, in the latest commit I enabled 'zero-copy' mode parameter for reading events.
It works fine both in the unit test and reading a production streamer file larger than 100 MB.

[smorovic]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-b93f17/26967/summary.html
COMMIT: d6ea8aa
CMSSW: CMSSW_12_5_X_2022-08-21-0000/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/39088/26967/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3693040
• DQMHistoTests: Total failures: 2
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3693016
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 212 log files, 49 edm output root files, 51 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 master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)

[makortel]

urgent

Just for @cms-sw/orp-l2 to note that it would be good to have this PR in pre5 so that Tier0 could potentially test the functionality soon (before it becomes part of a production release).

[perrotta]

+1