Merge remote-tracking branch 'origin/reshard' into next

* origin/reshard:
  xcpdb: support resharding v2 repos
  xcpdb: use destination shard as progress prefix
  xapcmd: preserve indexlevel based on the destination
  v2writable: use a smaller default for Xapian partitions

1 files changed, 16 insertions, 2 deletions

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 09ed4e7b..3329d79f 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -23,7 +23,14 @@ use IO::Handle;
 # 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
+# SATA storage lags behind what CPUs are capable of, so relying on
+# nproc(1) can be misleading and having extra Xapian partions is a
+# waste of FDs and space.  It can also lead to excessive IO latency
+# and slow things down.  Users on NVME or other fast storage can
+# use the NPROC env or switches in our script/public-inbox-* programs
+# to increase Xapian partitions.
+our $NPROC_MAX_DEFAULT = 4;
+
 sub nproc_parts ($) {
         my ($creat_opt) = @_;
         if (ref($creat_opt) eq 'HASH') {
@@ -32,7 +39,14 @@ sub nproc_parts ($) {
                 }
         }
 
-        my $n = int($ENV{NPROC} || `nproc 2>/dev/null` || 2);
+        my $n = $ENV{NPROC};
+        if (!$n) {
+                chomp($n = `nproc 2>/dev/null`);
+                # assume 2 cores if GNU nproc(1) is not available
+                $n = 2 if !$n;
+                $n = $NPROC_MAX_DEFAULT if $NPROC_MAX_DEFAULT > 4;
+        }
+
         # subtract for the main process and git-fast-import
         $n -= 1;
         $n < 1 ? 1 : $n;