CommonMessaging - Improved inlining and branch predicition

This MR includes a minor change to CommonMessaging.h designed to improve the runtime performance of CommonMessaging::setUpMessaging(), which is quite heavily called, by making a few trivial changes.

• The method CommonMessaging::setUpMessaging() is split in two, moving the part that is infrequently called to a new private method. This makes the footprint of CommonMessaging::setUpMessaging() much smaller and consequently improves the likelihood of it being inlined.
• I added an UNLIKELY( ) hint around the !m_commonMessagingReady to help the compiler better optimise the check branch prediction.

Together these MRs address a small performance regression I recently noticed, most likely due to !566 (merged). See the callgrind heat maps below for the cost of a given algorithm call, before and after the change.

Before :

After:

approved this merge request

• [2018-02-07 11:22] Validation started with lhcb-gaudi-merge#409
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• [2018-02-25 01:04] Validation started with lhcb-gaudi-head-py3#75
• [2018-02-25 01:06] Validation started with lhcb-tdr-test#70
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changed the description

added C++ framework label

added 9 commits

• c3c21a5e...bcfd63db - 8 commits from branch gaudi:master
• c7aed820 - Merge branch 'master' of ssh://gitlab.cern.ch:7999/gaudi/Gaudi into CommonMessaging-ImproveInlining

Compare with previous version

mentioned in merge request lhcb/Rec!889 (merged)

changed milestone to %v29r3

resolved all discussions

changed milestone to %v30r2

approved this merge request

assigned to @leggett

Does gitlab automatically squash all redundant merge commits? In the end, this MR is only 1 relevant commit, and not 102... would be good to avoid adding 101 redundant commits to the master...

No, unless you tick the "squash" checkbox before merging. Another possibility is to rebase.

added 28 commits

• c7aed820...5746b2fc - 27 commits from branch gaudi:master
• 0e1ef223 - Rework CommonMessaging::setUpMessaging() to improve runtime performance by…

Compare with previous version

Apologies... Have rebased so commit history is clean now.

approved this merge request