Toolchain very slow on Windows machines

[Peter Haas]

Dear Nordic Team,

we are using the adafruit_feather_nrf52840 and nrf52840dk for our prototypes and recently the toolchain around nrf and zephyr has become a problem.

Build times (especially compilation of the device tree according to logs) became very long such that one reload of our cmake project takes up to 15 minutes.

It had worked in reasonable time previously, at some point the toolchain slowed down on 2 individual machines.
This has happened on 2 different machines with 3 different versions of zephyr and the nrf toolchain (v2.6.0, v2.6.1, v2.7.0).

I tested using standalone zephyr for the build which doesn't seem to work trivially, however it does build an image in less than 10 seconds.
Also on a Linux machine I have available, the build times are much shorter.

Is anybody aware of any windows specific problems or problems with dtc.exe that may cause this?

Is there some cache we directory or temporal files we may have missed to clean?

We have been investigating for some time now as it really slows down our development iterations severely.

[Simonr]

Hmm, okay. Thank you. By stuck, does the terminal just pop up empty or does nothing happen at all when running dtc.exe?

One thing to try, as a colleague had an issue with slow build times as well, although I don't really think it's related, since I'm pretty sure your issue is firewall related. On their end it helped running git gc in .../<NCS_VERSION>/zephyr 

Best regards,

Simon

[Peter Haas]

By stuck I mean just the command line program doesn't return.
No output, no return code. 
Seemingly equivalent to just an empty infinite loop :) 

Git gc didn't help here.
To reiterate: Our temporal fix is just disconnecting the build machine from the network when building/flashing firmware.

Thanks!
Best,
Peter