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 [thread overview]
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
next prev parent reply other threads:[~2019-06-14 3:03 UTC|newest]
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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