[PATCH 07/16] lei: clamp internal worker processes to 4

[Eric Wong <e@80x24.org>]

"All" my CPUs is only 4, but it's probably ridiculous for
somebody with a 16-core system to have 16 processes for
accessing SQLite DBs.

We do the same thing in Pmdir for parallel Maildir access
(and V2Writable).
---
 lib/PublicInbox/LeiImportKw.pm  | 4 +++-
 lib/PublicInbox/LeiNoteEvent.pm | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/PublicInbox/LeiImportKw.pm b/lib/PublicInbox/LeiImportKw.pm
index 2863d17f..379101c2 100644
--- a/lib/PublicInbox/LeiImportKw.pm
+++ b/lib/PublicInbox/LeiImportKw.pm
@@ -11,7 +11,9 @@ use parent qw(PublicInbox::IPC);
 sub new {
 	my ($cls, $lei) = @_;
 	my $self = bless { -wq_ident => 'lei import_kw worker' }, $cls;
-	my ($op_c, $ops) = $lei->workers_start($self, $self->detect_nproc);
+	my $j = $self->detect_nproc // 4;
+	$j = 4 if $j > 4;
+	my ($op_c, $ops) = $lei->workers_start($self, $j);
 	$op_c->{ops} = $ops; # for PktOp->event_step
 	$self->{lei_sock} = $lei->{sock};
 	$lei->{ikw} = $self;
diff --git a/lib/PublicInbox/LeiNoteEvent.pm b/lib/PublicInbox/LeiNoteEvent.pm
index 5f692e75..a0591a09 100644
--- a/lib/PublicInbox/LeiNoteEvent.pm
+++ b/lib/PublicInbox/LeiNoteEvent.pm
@@ -80,8 +80,9 @@ sub lei_note_event {
 	my $self = $cfg->{-lei_note_event} //= do {
 		my $wq = bless { lms => $lms }, __PACKAGE__;
 		# MUAs such as mutt can trigger massive rename() storms so
-		# use all CPU power available:
+		# use some CPU, but don't overwhelm slower storage, either
 		my $jobs = $wq->detect_nproc // 1;
+		$jobs = 4 if $jobs > 4; # same default as V2Writable
 		my ($op_c, $ops) = $lei->workers_start($wq, $jobs);
 		$lei->wait_wq_events($op_c, $ops);
 		note_event_arm_done($lei);