diff --git a/command.py b/command.py
index 4087cab5..b972a0be 100644
--- a/command.py
+++ b/command.py
@@ -24,6 +24,10 @@ from error import InvalidProjectGroupsError
 import progress
 
 
+# Are we generating man-pages?
+GENERATE_MANPAGES = os.environ.get('_REPO_GENERATE_MANPAGES_') == ' indeed! '
+
+
 # Number of projects to submit to a single worker process at a time.
 # This number represents a tradeoff between the overhead of IPC and finer
 # grained opportunity for parallelism. This particular value was chosen by
@@ -122,10 +126,14 @@ class Command(object):
                  help='only show errors')
 
     if self.PARALLEL_JOBS is not None:
+      default = 'based on number of CPU cores'
+      if not GENERATE_MANPAGES:
+        # Only include active cpu count if we aren't generating man pages.
+        default = f'%default; {default}'
       p.add_option(
           '-j', '--jobs',
           type=int, default=self.PARALLEL_JOBS,
-          help='number of jobs to run in parallel (default: %s)' % self.PARALLEL_JOBS)
+          help=f'number of jobs to run in parallel (default: {default})')
 
   def _Options(self, p):
     """Initialize the option parser with subcommand-specific options."""
diff --git a/man/repo-abandon.1 b/man/repo-abandon.1
index fb3160c3..b3c0422f 100644
--- a/man/repo-abandon.1
+++ b/man/repo-abandon.1
@@ -20,7 +20,8 @@ It is equivalent to "git branch \fB\-D\fR <branchname>".
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-\-all\fR
 delete all branches in all projects
diff --git a/man/repo-branches.1 b/man/repo-branches.1
index 0080e467..7fe0b02d 100644
--- a/man/repo-branches.1
+++ b/man/repo-branches.1
@@ -46,7 +46,8 @@ is shown, then the branch appears in all projects.
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .SS Logging options:
 .TP
 \fB\-v\fR, \fB\-\-verbose\fR
diff --git a/man/repo-checkout.1 b/man/repo-checkout.1
index 882b4baf..6dd3e6ca 100644
--- a/man/repo-checkout.1
+++ b/man/repo-checkout.1
@@ -15,7 +15,8 @@ Checkout a branch for development
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .SS Logging options:
 .TP
 \fB\-v\fR, \fB\-\-verbose\fR
diff --git a/man/repo-diff.1 b/man/repo-diff.1
index aff36d24..890f8d22 100644
--- a/man/repo-diff.1
+++ b/man/repo-diff.1
@@ -19,7 +19,8 @@ to the Unix 'patch' command.
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-u\fR, \fB\-\-absolute\fR
 paths are relative to the repository root
diff --git a/man/repo-forall.1 b/man/repo-forall.1
index 194f4d20..eb2ad57b 100644
--- a/man/repo-forall.1
+++ b/man/repo-forall.1
@@ -17,7 +17,8 @@ repo forall \fB\-r\fR str1 [str2] ... \fB\-c\fR <command> [<arg>...]
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-r\fR, \fB\-\-regex\fR
 execute the command only on projects matching regex or
diff --git a/man/repo-grep.1 b/man/repo-grep.1
index fb515a7b..be410588 100644
--- a/man/repo-grep.1
+++ b/man/repo-grep.1
@@ -15,7 +15,8 @@ Print lines matching a pattern
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .SS Logging options:
 .TP
 \fB\-\-verbose\fR
diff --git a/man/repo-prune.1 b/man/repo-prune.1
index 2479542c..bd68a373 100644
--- a/man/repo-prune.1
+++ b/man/repo-prune.1
@@ -15,7 +15,8 @@ Prune (delete) already merged topics
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .SS Logging options:
 .TP
 \fB\-v\fR, \fB\-\-verbose\fR
diff --git a/man/repo-smartsync.1 b/man/repo-smartsync.1
index ad98b479..5d939117 100644
--- a/man/repo-smartsync.1
+++ b/man/repo-smartsync.1
@@ -15,7 +15,8 @@ Update working tree to the latest known good revision
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 1)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-\-jobs\-network\fR=\fI\,JOBS\/\fR
 number of network jobs to run in parallel (defaults to
diff --git a/man/repo-start.1 b/man/repo-start.1
index cda3739f..b00a31f4 100644
--- a/man/repo-start.1
+++ b/man/repo-start.1
@@ -15,7 +15,8 @@ Start a new branch for development
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-\-all\fR
 begin branch in all projects
diff --git a/man/repo-status.1 b/man/repo-status.1
index 6037ae1a..fbae2c5d 100644
--- a/man/repo-status.1
+++ b/man/repo-status.1
@@ -15,7 +15,8 @@ Show the working tree status
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-o\fR, \fB\-\-orphans\fR
 include objects in working directory outside of repo
diff --git a/man/repo-sync.1 b/man/repo-sync.1
index 70f7c207..c87c9701 100644
--- a/man/repo-sync.1
+++ b/man/repo-sync.1
@@ -15,7 +15,8 @@ Update working tree to the latest revision
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 1)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-\-jobs\-network\fR=\fI\,JOBS\/\fR
 number of network jobs to run in parallel (defaults to
diff --git a/man/repo-upload.1 b/man/repo-upload.1
index 6deed047..36a0daca 100644
--- a/man/repo-upload.1
+++ b/man/repo-upload.1
@@ -15,7 +15,8 @@ Upload changes for code review
 show this help message and exit
 .TP
 \fB\-j\fR JOBS, \fB\-\-jobs\fR=\fI\,JOBS\/\fR
-number of jobs to run in parallel (default: 4)
+number of jobs to run in parallel (default: based on
+number of CPU cores)
 .TP
 \fB\-t\fR
 send local branch name to Gerrit Code Review
diff --git a/release/update-manpages b/release/update-manpages
index f841f306..6ef3ec11 100755
--- a/release/update-manpages
+++ b/release/update-manpages
@@ -47,6 +47,11 @@ def main(argv):
   if not shutil.which('help2man'):
     sys.exit('Please install help2man to continue.')
 
+  # Let repo know we're generating man pages so it can avoid some dynamic
+  # behavior (like probing active number of CPUs).  We use a weird name &
+  # value to make it less likely for users to set this var themselves.
+  os.environ['_REPO_GENERATE_MANPAGES_'] = ' indeed! '
+
   # "repo branch" is an alias for "repo branches".
   del subcmds.all_commands['branch']
   (MANDIR / 'repo-branch.1').write_text('.so man1/repo-branches.1')