lib/PublicInbox/V2Writable.pm | 13 +++++++++++--
 script/public-inbox-index     |  3 +--
 t/purge.t                     |  3 +--
 t/v2reindex.t                 |  3 +--
 t/v2writable.t                |  8 ++------

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index b92d8d247b8d0b689e67159911d736b3c2a49289..afcac4d2db863103f5e92dfd82bbbeb5301279a5 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -24,7 +24,14 @@ # an estimate of the post-packed size to the raw uncompressed size
 my $PACKING_FACTOR = 0.4;
 
 # assume 2 cores if GNU nproc(1) is not available
-sub nproc_parts () {
+sub nproc_parts ($) {
+	my ($creat_opt) = @_;
+	if (ref($creat_opt) eq 'HASH') {
+		if (defined(my $n = $creat_opt->{nproc})) {
+			return $n
+		}
+	}
+
 	my $n = int($ENV{NPROC} || `nproc 2>/dev/null` || 2);
 	# subtract for the main process and git-fast-import
 	$n -= 1;
@@ -52,6 +59,8 @@ 	$nparts;
 }
 
 sub new {
+	# $creat may be any true value, or 0/undef.  A hashref is true,
+	# and $creat->{nproc} may be set to an integer
 	my ($class, $v2ibx, $creat) = @_;
 	my $dir = $v2ibx->{mainrepo} or die "no mainrepo in inbox\n";
 	unless (-d $dir) {
@@ -80,7 +89,7 @@ 		# limit each git repo (epoch) to 1GB or so
 		rotate_bytes => int((1024 * 1024 * 1024) / $PACKING_FACTOR),
 		last_commit => [], # git repo -> commit
 	};
-	$self->{partitions} = count_partitions($self) || nproc_parts();
+	$self->{partitions} = count_partitions($self) || nproc_parts($creat);
 	bless $self, $class;
 }
 
diff --git a/script/public-inbox-index b/script/public-inbox-index
index 2f810a564f01367a592c0862705074e077a193c9..b353093e49250e2296f6c12edaee656dd40fb064 100755
--- a/script/public-inbox-index
+++ b/script/public-inbox-index
@@ -71,8 +71,7 @@ 	if (ref($repo) && ($repo->{version} || 1) == 2) {
 		eval { require PublicInbox::V2Writable };
 		die "v2 requirements not met: $@\n" if $@;
 		my $v2w = eval {
-			$jobs and local $ENV{NPROC} = $jobs;
-			PublicInbox::V2Writable->new($repo);
+			PublicInbox::V2Writable->new($repo, {nproc=>$jobs});
 		};
 		if (defined $jobs) {
 			if ($jobs == 0) {
diff --git a/t/purge.t b/t/purge.t
index b518c26fb0aab488042547c2982c68bdfa9108d0..574935e08e72f1b01eb5700e6a07ba38952d0cb1 100644
--- a/t/purge.t
+++ b/t/purge.t
@@ -35,12 +35,11 @@ Hello World
 
 EOF
 
-local $ENV{NPROC} = '1';
 my $cfgfile = "$tmpdir/config";
 local $ENV{PI_CONFIG} = $cfgfile;
 open my $cfg_fh, '>', $cfgfile or die "open: $!";
 
-my $v2w = PublicInbox::V2Writable->new($ibx, 1);
+my $v2w = PublicInbox::V2Writable->new($ibx, {nproc => 1});
 my $mime = PublicInbox::MIME->new($raw);
 ok($v2w->add($mime), 'add message to be purged');
 $v2w->done;
diff --git a/t/v2reindex.t b/t/v2reindex.t
index 8a3071b734af5c763a8192cfafd74e3919e57f7a..c416629c3f4155cc5bc0e5642f64a9b4952747fd 100644
--- a/t/v2reindex.t
+++ b/t/v2reindex.t
@@ -39,14 +39,13 @@ 		Date => 'Fri, 02 Oct 1993 00:00:00 +0000',
 	],
 	body => $agpl,
 );
-local $ENV{NPROC} = 2;
 my $minmax;
 my $msgmap;
 my ($mark1, $mark2, $mark3, $mark4);
 {
 	my %config = %$ibx_config;
 	my $ibx = PublicInbox::Inbox->new(\%config);
-	my $im = PublicInbox::V2Writable->new($ibx, 1);
+	my $im = PublicInbox::V2Writable->new($ibx, {nproc => 1});
 	my $im0 = $im->importer();
 	foreach my $i (1..10) {
 		$mime->header_set('Message-Id', "<$i\@example.com>");
diff --git a/t/v2writable.t b/t/v2writable.t
index f8ef415acc51061b30fbd006ee491edb74c7c536..75110155f3fa9bc0f0729e9acaf828740b79e0d3 100644
--- a/t/v2writable.t
+++ b/t/v2writable.t
@@ -33,10 +33,7 @@ 	],
 	body => "hello world\n",
 );
 
-my $im = eval {
-	local $ENV{NPROC} = '1';
-	PublicInbox::V2Writable->new($ibx, 1);
-};
+my $im = PublicInbox::V2Writable->new($ibx, {nproc => 1});
 is($im->{partitions}, 1, 'one partition when forced');
 ok($im->add($mime), 'ordinary message added');
 foreach my $f ("$mainrepo/msgmap.sqlite3",
@@ -201,11 +198,10 @@ 	my $rover = $n->xrover('1-');
 	is_deeply([sort keys %lg], [sort keys %$rover], 'XROVER range OK');
 };
 {
-	local $ENV{NPROC} = 2;
 	my @log = qw(log --no-decorate --no-abbrev --no-notes --no-color);
 	my @before = $git0->qx(@log, qw(--pretty=oneline));
 	my $before = $git0->qx(@log, qw(--pretty=raw --raw -r));
-	$im = PublicInbox::V2Writable->new($ibx, 1);
+	$im = PublicInbox::V2Writable->new($ibx, {nproc => 2});
 	is($im->{partitions}, 1, 'detected single partition from previous');
 	my $smsg = $im->remove($mime, 'test removal');
 	$im->done;