On 03/18/18 19:28, Daniel Gustafsson wrote:
> It seems expensive to regex over BLCKSZ, but it’s probably the safest option
> and it’s not a performance critical codepath. Feel free to whack the test
> patch over the head with the above diff.
Both patches in a single email for cfbot's enjoyment, coming right up.
-Chap
>From b2d36e3e4f4cd003cd7564a217bb15c19e1da5e2 Mon Sep 17 00:00:00 2001
From: Chapman Flack <c...@anastigmatix.net>
Date: Sun, 18 Mar 2018 20:03:04 -0400
Subject: [PATCH] Add test for ensuring WAL segment is zeroed out
Switch to a new WAL file and ensure the last block in the now
switched-away-from file is completely zeroed out.
This adds a mode to check_pg_config() where the match from the
regexp can be returned, not just the literal count of matches.
Only one match is returned (the first), but given the structure
of pg_config.h that's likely to be enough.
---
.travis.yml | 47 ++++++++++++++++++++++++++++++++++++
src/test/perl/TestLib.pm | 18 ++++++++++++--
src/test/recovery/t/002_archiving.pl | 19 ++++++++++++++-
3 files changed, 81 insertions(+), 3 deletions(-)
create mode 100644 .travis.yml
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..386bb60
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,47 @@
+
+sudo: required
+addons:
+ apt:
+ packages:
+ - gdb
+ - lcov
+ - libipc-run-perl
+ - libperl-dev
+ - libpython-dev
+ - tcl-dev
+ - libldap2-dev
+ - libicu-dev
+ - docbook
+ - docbook-dsssl
+ - docbook-xsl
+ - libxml2-utils
+ - openjade1.3
+ - opensp
+ - xsltproc
+language: c
+cache: ccache
+before_install:
+ - echo '/tmp/%e-%s-%p.core' | sudo tee /proc/sys/kernel/core_pattern
+ - echo "deb http://archive.ubuntu.com/ubuntu xenial main" | sudo tee /etc/apt/sources.list.d/xenial.list > /dev/null
+ - |
+ sudo tee -a /etc/apt/preferences.d/trusty > /dev/null <<EOF
+ Package: *
+ Pin: release n=xenial
+ Pin-Priority: 1
+
+ Package: make
+ Pin: release n=xenial
+ Pin-Priority: 500
+ EOF
+ - sudo apt-get update && sudo apt-get install make
+script: ./configure --enable-debug --enable-cassert --enable-coverage --enable-tap-tests --with-tcl --with-python --with-perl --with-ldap --with-icu && make -j4 all contrib docs && make -Otarget -j3 check-world
+after_success:
+ - bash <(curl -s https://codecov.io/bash)
+after_failure:
+ - for f in ` find . -name regression.diffs ` ; do echo "========= Contents of $f" ; head -1000 $f ; done
+ - |
+ for corefile in $(find /tmp/ -name '*.core' 2>/dev/null) ; do
+ binary=$(gdb -quiet -core $corefile -batch -ex 'info auxv' | grep AT_EXECFN | perl -pe "s/^.*\"(.*)\"\$/\$1/g")
+ echo dumping $corefile for $binary
+ gdb --batch --quiet -ex "thread apply all bt full" -ex "quit" $binary $corefile
+ done
diff --git a/src/test/perl/TestLib.pm b/src/test/perl/TestLib.pm
index 7d017d4..8b9796c 100644
--- a/src/test/perl/TestLib.pm
+++ b/src/test/perl/TestLib.pm
@@ -227,15 +227,29 @@ sub append_to_file
# that.
sub check_pg_config
{
- my ($regexp) = @_;
+ my ($regexp, $value) = @_;
my ($stdout, $stderr);
+ my $match;
my $result = IPC::Run::run [ 'pg_config', '--includedir' ], '>',
\$stdout, '2>', \$stderr
or die "could not execute pg_config";
chomp($stdout);
open my $pg_config_h, '<', "$stdout/pg_config.h" or die "$!";
- my $match = (grep {/^$regexp/} <$pg_config_h>);
+ if (defined $value)
+ {
+ while (<$pg_config_h>)
+ {
+ $_ =~ m/^$regexp/;
+ next unless defined $1;
+ $match = $1;
+ last;
+ }
+ }
+ else
+ {
+ $match = (grep {/^$regexp/} <$pg_config_h>);
+ }
close $pg_config_h;
return $match;
}
diff --git a/src/test/recovery/t/002_archiving.pl b/src/test/recovery/t/002_archiving.pl
index e1bd3c9..9551db1 100644
--- a/src/test/recovery/t/002_archiving.pl
+++ b/src/test/recovery/t/002_archiving.pl
@@ -3,7 +3,7 @@ use strict;
use warnings;
use PostgresNode;
use TestLib;
-use Test::More tests => 1;
+use Test::More tests => 2;
use File::Copy;
# Initialize master node, doing archives
@@ -49,3 +49,20 @@ $node_standby->poll_query_until('postgres', $caughtup_query)
my $result =
$node_standby->safe_psql('postgres', "SELECT count(*) FROM tab_int");
is($result, qq(1000), 'check content from archives');
+
+# Add some content, switch WAL file and read the last segment of the WAL
+# file which should be zeroed out
+my $current_file = $node_master->safe_psql('postgres',
+ "SELECT pg_walfile_name(pg_current_wal_lsn())");
+$node_master->safe_psql('postgres', "INSERT INTO tab_int VALUES (1)");
+$node_master->safe_psql('postgres', "SELECT pg_switch_wal()");
+
+my $xlog_blcksz = check_pg_config('#define XLOG_BLCKSZ (\d+)', 1);
+
+open my $fh, '<:raw', $node_master->data_dir . '/pg_wal/' . $current_file;
+# SEEK_END is defined as 2, but is not allowed when using strict mode
+seek $fh, ($xlog_blcksz * -1), 2;
+my $len = read($fh, my $bytes, $xlog_blcksz);
+close $fh;
+
+ok($bytes =~ /\A\x00*+\z/, 'make sure wal segment is zeroed');
--
2.7.3
From 35684bdaa1d27c3f4b7198541f3c92bb2b4cb2f4 Mon Sep 17 00:00:00 2001
From: Chapman Flack <c...@anastigmatix.net>
Date: Sun, 25 Feb 2018 11:44:47 -0500
Subject: [PATCH] Zero headers of unused pages after WAL switch.
When writing zeroed pages to the remainder of a WAL segment
after a WAL switch, ensure that the headers of those pages are
also zeroed, as their initialized values otherwise reduce the
compressibility of the WAL segment file by general tools.
---
src/backend/access/transam/xlog.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/src/backend/access/transam/xlog.c
b/src/backend/access/transam/xlog.c
index 47a6c4d..a91ec7b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1556,7 +1556,16 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch,
XLogRecData *rdata,
{
/* initialize the next page (if not initialized
already) */
WALInsertLockUpdateInsertingAt(CurrPos);
- AdvanceXLInsertBuffer(CurrPos, false);
+ /*
+ * Fields in the page header preinitialized by
AdvanceXLInsertBuffer
+ * to nonconstant values reduce the compressibility of
WAL segments,
+ * and aren't needed in the freespace following a
switch record.
+ * Re-zero that header area. This is not
performance-critical, as
+ * the more empty pages there are for this loop to
touch, the less
+ * busy the system is.
+ */
+ currpos = GetXLogBuffer(CurrPos);
+ MemSet(currpos, 0, SizeOfXLogShortPHD);
CurrPos += XLOG_BLCKSZ;
}
}
--
2.7.3
