Description of problem:
1) Minimal observed inc. build time is ~20s, which is not what I would expect from "incremental" build. It should be faster than complete project build, shouldn't it?

2) More importantly, the time increases as commits cumulate in system.git repository. When my system.git grew close to 2000 commits[1], the incremental build for mortgages duration reached 60s for any DRL rule. After deleting system.git and server restart, inc. build time dropped back to ~20s.

Version-Release number of selected component (if applicable):
ER3

How reproducible:
-

Steps to Reproduce:
1. open Dummy rule in mortgages
2. repeatedly save the file and observe the duration of incremental build in server log, or the time before save success notification appears (the notification is blocked by running inc. build)

Actual results:
After 180 save iterations the inc. build time (and time between save notifications) increased from 24s to ~75s. Then I created a new rule and made a few more saves, which took ~60s too.

Expected results:
1) The incremental build should be significantly faster (a few seconds at most).
2) Inc. build time shouldn't increase with history size of either the file which triggered the build, the repository it belongs to, or system.git repository.

Additional info:
Not only incremental build is getting slower as system.git grows. Switching to authoring perspective and navigating between repositories, projects and packages in Project Explorer is evidently slower, too.

[1] Most of the commits are inbox updates (recently viewed, recently edited etc.).