Michael Albinus wrote:

>>  Let's mark the slow tests to be expensive, so that they are run only
>> if one executes "make check-expensive".
>
> This is already the case. I guess you've uncovered an error, which must
> be fixed.

I think he meant that more tests should be marked expensive.
From the nice new timing feature that you added:

20 slowest non-expensive tests:
2.107192 auto-revert-test03-auto-revert-tail-mode
2.185436 included-c-header-files
2.478982 tramp-test09-insert-file-contents
2.539473 tramp-test39-utf8
2.541236 tramp-test15-copy-directory
2.641033 tramp-test08-file-local-copy
3.053811 file-notify-test05-file-validity
3.057267 file-notify-test08-backup
3.238807 file-notify-test03-events
3.453809 tramp-archive-test42-auto-load
5.005737 inotify-file-watch-simple
5.270187 tramp-test10-write-region
6.005597 file-notify-test04-autorevert
6.067378 auto-revert-test04-auto-revert-mode-dired
7.129754 cl-seq-test-bug24264
7.696874 tramp-test38-special-characters
12.318760 tramp-test12-rename-file
12.621092 tramp-test11-copy-file
13.105928 auto-revert-test00-auto-revert-mode
22.254235 tramp-test21-file-links

20 slowest expensive tests:
2.443189 file-notify-test06-dir-validity-remote
2.499095 tramp-test39-utf8-with-stat
2.581147 tramp-test39-utf8-with-ls
3.058655 tramp-test39-utf8-with-perl
3.140859 auto-revert-test01-auto-revert-several-files
3.741687 tramp-test41-asynchronous-requests
4.417266 file-notify-test05-file-validity-remote
4.454070 file-notify-test01-add-watch-remote
4.894808 file-notify-test08-backup-remote
4.983632 file-notify-test02-rm-watch-remote
7.111716 auto-revert-test02-auto-revert-deleted-file
7.502341 file-notify-test04-autorevert-remote
8.159349 tramp-test38-special-characters-with-stat
8.347577 tramp-test38-special-characters-with-ls
10.124505 tramp-test38-special-characters-with-perl
10.138312 file-notify-test09-watched-file-in-watched-dir
10.299857 file-notify-test03-events-remote
34.731760 ucs-normalize-part1
43.038078 file-notify-test07-many-events
579.167091 file-notify-test07-many-events-remote