I did some tests - following is what is logged if I use Preferences->Restart in debug mode.
Code:
calibre Debug log
calibre 3.16 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.15063-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.15063')
Python 2.7.12+
Windows: ('10', '10.0.15063', 'SP0', u'Multiprocessor Free')
Interface language: None
DEBUG: 0.0 GetFileName::__init__.py - loading translations
DEBUG: 0.0 GetFileName::__init__.py - loading translations
Successfully initialized third party plugins: User Category (1, 5, 3) && Job Spy (1, 0, 97) && Goodreads (1, 1, 13) && Extract ISBN (1, 4, 4) && Quality Check (1, 9, 11) && Count Pages (1, 8, 0) && Drop Search Results (1, 0, 8) && Reading List (1, 6, 6) && Find Duplicates (1, 6, 3) && View Manager (1, 3, 2) && Modify ePub (1, 3, 13) && Generate Cover (1, 5, 21) && Favourites Menu (1, 0, 4) && Resize Cover (1, 0, 3) && EpubSplit (2, 3, 0) && Beam Ebooks (1, 0, 0) && Barnes & Noble (1, 2, 14) && GetFileName (0, 0, 12)
calibre 3.16 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.15063-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.15063')
Python 2.7.12+
Windows: ('10', '10.0.15063', 'SP0', u'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: User Category (1, 5, 3) && Job Spy (1, 0, 97) && Goodreads (1, 1, 13) && Extract ISBN (1, 4, 4) && Quality Check (1, 9, 11) && Count Pages (1, 8, 0) && Drop Search Results (1, 0, 8) && Reading List (1, 6, 6) && Find Duplicates (1, 6, 3) && View Manager (1, 3, 2) && Modify ePub (1, 3, 13) && Generate Cover (1, 5, 21) && Favourites Menu (1, 0, 4) && Resize Cover (1, 0, 3) && EpubSplit (2, 3, 0) && Beam Ebooks (1, 0, 0) && Barnes & Noble (1, 2, 14) && GetFileName (0, 0, 12)
Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 120.0 x 120.0
physicalDpi: 123.385199241 x 123.567567568
Using calibre Qt style: True
Starting up...
Job Spy has begun initialization...
author_sort_copy_method >>> default tweaks.py method is: copy
author_sort_copy_method changed FROM: copy TO: comma
Calibre, and hence Job Spy, was gracefully shut down last time? True
Last time daemon started: never
Last time daemon failed: never
Total daemon starts inception_to_date: 0
Total daemon failures inception-to-date: 0
Job Spy has finished initialization...
Started up in 2.43 seconds with 3 books
Interestingly, there's some debug printf's from GetFileName in the first 'start', but not in the second.
And this is what I get if I run "calibre-debug -g 1 >> calibrelog.txt 2>&1" from a command line.
Code:
calibre 3.16 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.15063-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.15063')
Python 2.7.12+
Windows: ('10', '10.0.15063', 'SP0', u'Multiprocessor Free')
Interface language: None
DEBUG: 0.0 GetFileName::__init__.py - loading translations
DEBUG: 0.0 GetFileName::__init__.py - loading translations
Successfully initialized third party plugins: Extract ISBN (1, 4, 4) && Beam Ebooks (1, 0, 0) && Drop Search Results (1, 0, 8) && Count Pages (1, 8, 0) && Favourites Menu (1, 0, 4) && Goodreads (1, 1, 13) && Resize Cover (1, 0, 3) && Quality Check (1, 9, 11) && Modify ePub (1, 3, 13) && Generate Cover (1, 5, 21) && Barnes & Noble (1, 2, 14) && EpubSplit (2, 3, 0) && Reading List (1, 6, 6) && Job Spy (1, 0, 97) && GetFileName (0, 0, 12) && Find Duplicates (1, 6, 3) && View Manager (1, 3, 2) && User Category (1, 5, 3)
Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 120.0 x 120.0
physicalDpi: 123.385199241 x 123.567567568
Using calibre Qt style: True
Starting up...
libpng warning: iCCP: known incorrect sRGB profile
Job Spy has begun initialization...
author_sort_copy_method >>> default tweaks.py method is: copy
author_sort_copy_method changed FROM: copy TO: comma
Calibre, and hence Job Spy, was gracefully shut down last time? True
Last time daemon started: never
Last time daemon failed: never
Total daemon starts inception_to_date: 0
Total daemon failures inception-to-date: 0
libpng warning: iCCP: known incorrect sRGB profile
Job Spy has finished initialization...
Started up in 2.52 seconds with 3 books
I've not noticed the 'stuttering start' being logged before, but I rarely start in debug mode, from the command line or via Shift+Ctrl+R. When I first saw the OPs log I thought -- that looks a bit odd, but I shrugged and moved on.
Turning the splash screen on increased start times from 2.xx secs to 5.xx secs.
Yes I'm still using 3.16, I'm awaiting for any further developments re Split Book List and View Manager, I use an old version of View Manager and I haven't had time to see how it interacts with Split List.
BR