Bug 540615

Summary: PDE: callOnEmptyDelta for PDE builders breaks small deltas with many projects
Product: [Eclipse Project] PDE Reporter: Markus Duft <markus.duft>
Component: BuildAssignee: Markus Duft <markus.duft>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: P3 CC: karsten.thoms, loskutov
Version: 4.8Keywords: performance, regression
Target Milestone: 4.10 M3   
Hardware: PC   
OS: All   
See Also: https://git.eclipse.org/r/131658
https://bugs.eclipse.org/bugs/show_bug.cgi?id=527016
https://git.eclipse.org/c/pde/eclipse.pde.ui.git/commit/?id=3b18435a0262f52ee5504f6554dfc6cbb20d6268
Whiteboard:

Description Markus Duft CLA 2018-10-30 11:48:12 EDT 
The fix for 527016 set all PDE builders to run even on empty deltas to avoid the computation of delta trees for large deltas.

For workspaces with many projects (~750 in our case) this is a major performance issue, as commented on 527016 as well.

At least for us the small delta use case (a manual change to a file) is the vast majority of deltas. Large deltas happen when rebasing (etc.), which is acceptable (IMHO) to take a little longer. Small deltas must be as fast as possible.

Reverting https://git.eclipse.org/r/#/c/111258/ locally immediately returns our Eclipse to a working state (i.e. autobuild after changing a single file takes <1 second vs. >30 seconds).
Comment 1 Eclipse Genie CLA 2018-10-30 11:49:50 EDT 
New Gerrit change created: https://git.eclipse.org/r/131658
Comment 2 Andrey Loskutov CLA 2018-10-30 12:06:39 EDT 
(In reply to Eclipse Genie from comment #1)
> New Gerrit change created: https://git.eclipse.org/r/131658

Bug 527016 comment 7 says "the effect is minimal", so I would also agree to revert to the old state, since it can cause such critical regressions like here.

@Karsten: any objections?
Comment 3 Karsten Thoms CLA 2018-10-30 13:52:53 EDT 
> @Karsten: any objections?

No, sounds reasonable. My bad.
Comment 5 Karsten Thoms CLA 2018-10-30 13:55:11 EDT 
Thanks, Markus!