user/dev discussion of public-inbox itself
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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 1/4] v2writable: use a smaller default for Xapian partitions
Date: Fri, 14 Jun 2019 03:03:15 +0000
Message-ID: <20190614030318.17216-2-e@80x24.org> (raw)
In-Reply-To: <20190614030318.17216-1-e@80x24.org>

Apparently 16 CPUs (probably HT) and SATA storage is common
these days.  Having excessive Xapian partitions leads to
contention and excessive FD/space use.  So set a smaller
default but continue allowing user-specified values to bump
this up.
---
 lib/PublicInbox/V2Writable.pm | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index a8c33ef..c504651 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;
-- 
EW


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14  3:03 [PATCH 0/4] xcpdb: support resharding Xapian DBs Eric Wong
2019-06-14  3:03 ` Eric Wong [this message]
2019-06-14  3:03 ` [PATCH 2/4] xapcmd: preserve indexlevel based on the destination Eric Wong
2019-06-14  3:03 ` [PATCH 3/4] xcpdb: use destination shard as progress prefix Eric Wong
2019-06-14  3:03 ` [PATCH 4/4] xcpdb: support resharding v2 repos Eric Wong

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