If is use
code . in terminal or just open vs code from menu, it is taking almost 15 to 20 seconds to open. I'm using Ubuntu 18.10 in Ideapad 100 with i3 5005u 8GB ram and SAMSUNG 850 evo 250GB ssd.
First step would be to ensure you Samsung 850 Evo is working up to capacity.
hdparm command to reveal speed:
$ sudo hdparm -tT /dev/nvme0n1p1 /dev/nvme0n1p1: Timing cached reads: 22162 MB in 2.00 seconds = 11095.29 MB/sec Timing buffered disk reads: 450 MB in 0.20 seconds = 2279.92 MB/sec
If the last line is less than say 1500 MB/sec you might have a problem. There are a number of places you can check to bumping up Samsung 850 EVO speed in Linux. Here is one example: Samsung SSD 850 Pro slow speed