"Go To Symbol in Workspace..." searchs are not "snappy" on large projects #7914

Bug type: Language Service

OS and Version: Windows10 (Version 2004)
VS Code Version: 1.58.2
C/C++ Extension Version: v1.5.1
"Go To Symbol in Workspace..."(CTRL+T) is very slow on large projects.

As a benchmark, I opened a workspace on Linux code base, and searched for "memory".
Results for the first search are abnormally long (~25 seconds). to be handled in another bug report (#7980)

Results for additinal searchs are around ~3s.
Since browsing large code bases requires many such searches, non-instant results becomes a burden.

Notes:

I set C_Cpp.intelliSenseEngine to "Tag Parser" (my preferred choice)
The workspace was fully parsed before running the search.
For comparison, on ** Source Insight IDE , results for the same symbol search are instant (<1s).**

Expected behavior
Full Workspace Symbols Search should return results faster (<1s)