Very slow configure run on 64-bit Windows 7

[Steve Fink]

I am using VirtualBox to host a 64-bit Windows 7 build box for compiling Firefox, and the configure step is mind-numbingly slow.

Host: Fedora 13 x86_64 with 12GB RAM, 8 cores (+ 8 hyperthreaded), 2.27GHz Guest: Windows 7 64-bit

I'm testing by running ./config.status at the toplevel (using the MozillaBuild msys build environment). I aborted after several hours, and switched to timing running js/src/config.status, which works on a much smaller subset of the tree.

On hardware, this took a few seconds to run. On my VM, it took 19.9seconds when giving the guest 4GB of RAM and 4 CPUs. The build directory was shared via guest additions with the host.

If I dropped the memory to 1GB RAM, it slowed down to 21sec. Dropping to 1 CPU sped it up. Switching to a Samba share sped it up. The fastest run I could get was 11.3sec.

In the fastest configuration, I tried the toplevel config.status again. It took 13.5 minutes; much faster but still far slower than hardware.

I have disabled Windows Defender, all the virus checkers I could find, and lots of stuff carried over from when it was a physical machine.

The guest CPU or CPUs are all pretty much maxed out during this test. When running with 4 guest CPUs, the real CPUs show about 25% utilization for half the CPUs, <2% for the other half. Neither the host nor the guest show significant disk or network I/O.

This configure test starts up many, many processes through the msys shell.