diff --git a/build/fbcode_builder/getdeps/buildopts.py b/build/fbcode_builder/getdeps/buildopts.py
index 480d8d799..83295b06d 100644
--- a/build/fbcode_builder/getdeps/buildopts.py
+++ b/build/fbcode_builder/getdeps/buildopts.py
@@ -83,6 +83,14 @@ class BuildOptions(object):
             import multiprocessing
 
             num_jobs = multiprocessing.cpu_count()
+            if is_windows():
+                # On Windows the cpu count tends to be the HT count.
+                # Running with that level of concurrency tends to
+                # swamp the system and make hard to perform other
+                # light work.  Let's halve the number of cores here
+                # to win that back. The user can still specify a
+                # larger number if desired.
+                num_jobs = int(num_jobs / 2)
 
         if not install_dir:
             install_dir = os.path.join(scratch_dir, "installed")