re: kern/56329: nvme(4) takes long time to umount

[matthew green <mrg%eterna.com.au@localhost>]

>  Finally got a laptop with
>      nvme0: SAMSUNG MZVLB256HAHQ-000L7, firmware 0L2QEXD7, serial S41GNB0K593889
>  and see unmount times of 10 .. 12 seconds with a DIAGNOSTIC + DEBUG + LOCKDEBUG
>  kernel.  All this time is spent in the first vflush().
>  
>  On a GENERIC kernel without DIAGNOSTIC etc the unmount time goes down to less
>  than a second and the disk becomes much faster.
>  
>  What kind of kernel are/were you using?

FWIW, i see this problem on non-nvme sometimes too, and it
seems related to how much data was written between booting
and shutdown.

DIAGNOSTIC shouldn't affect speed nearly this much!  code
like that should be in DEBUG probably.


.mrg.