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Diffstat (limited to 'scripts')
| -rwxr-xr-x | scripts/mc_slab_mover | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/scripts/mc_slab_mover b/scripts/mc_slab_mover new file mode 100755 index 0000000..d7bd5e4 --- /dev/null +++ b/scripts/mc_slab_mover @@ -0,0 +1,260 @@ +#! /usr/bin/perl +# See memcached for LICENSE +# Copyright 2011 Dormando (dormando@rydia.net) + +=head1 NAME + +mc_slab_mover -- example utility for slab page reassignment for memcached + +=head1 SYNOPSIS + + $ mc_slab_mover --host="127.0.0.1:11211" --verbose + $ mc_slab_mover --host="127.0.0.1:11211" --automove + $ mc_slab_mover --host="127.0.0.1:11211" --sleep=60 --loops=4 --automove + +=head1 DESCRIPTION + +This utility is an example implementation of an algorithm for reassigning +slab memory in a running memcached instance. If memcached's built-in +automover isn't working for you, you may use this script as an example +base and expand on it. We welcome modifications or alternatives on the +mailing list. + +=head1 ALGORITHM + +The default algorithm is simple, and may serve for a common case: over +time one slab may grow in use compare to others, and as evictions stop +in one slab and start in another it will reassign memory. + +If a slab has the most evictions three times in a row, it will pull a page +from a slab which has had zero evictions three times in a row. + +There are many traffic patterns where this does not work well. IE: If you +never use expirations and rely on the LRU (so all slabs always evict), +it will not be as likely to find source pages to move. + +=head1 OPTIONS + +=over + +=item --host="IP:PORT" + +The hostname to connect to. NOTE: If connection to the host breaks, script +will stop. + +=item --sleep=10 + +How long to wait between loops for gathering stats. + +=item --loops=3 + +How many loops to run before making a decision for a move. + +=item --verbose + +Prints a formatted dump of some common statistics per loop. + +=item --automove + +Enables the automover, and will attempt to move memory around if it finds +viable candidates. + +=back + +=head1 AUTHOR + +Dormando E<lt>L<dormando@rydia.net>E<gt> + +=head1 LICENSE + +Licensed for use and redistribution under the same terms as Memcached itself. + +=cut + +use warnings; +use strict; + +use IO::Socket::INET; + +use FindBin; +use Data::Dumper qw/Dumper/; +use Getopt::Long; + +my %opts = ('sleep' => 10, automove => 0, verbose => 0, loops => 3); +GetOptions( + "host=s" => \$opts{host}, + "sleep=i" => \$opts{'sleep'}, + "loops=i" => \$opts{loops}, + "automove" => \$opts{automove}, + "verbose" => \$opts{verbose}, + ) or usage(); + +die "Must specify at least --host='127.0.0.1:11211'" unless $opts{host}; +my $sock = IO::Socket::INET->new(PeerAddr => $opts{host}, + Timeout => 3); +die "$!\n" unless $sock; + +my %stats = (); +my %move = (winner => 0, wins => 0); + +$SIG{INT} = sub { + print "STATS: ", Dumper(\%stats), "\n"; + exit; +}; +$SIG{USR1} = sub { + print "STATS: ", Dumper(\%stats), "\n"; +}; +run(); + +sub usage { + print qq{Usage: + mc_slab_ratios --host="127.0.0.1:11211" --verbose --automove + run `perldoc mc_slab_ratios` for full information + +}; + exit 1; +} + +sub run { + my $slabs_before = grab_stats(); + + while (1) { + sleep $opts{'sleep'}; + my $slabs_after = grab_stats(); + + my ($totals, $sorted) = calc_results_evicted($slabs_before, $slabs_after); +# my ($totals, $sorted) = calc_results_numratio($slabs_before, $slabs_after); + + my $pct = sub { + my ($num, $divisor) = @_; + return 0 unless $divisor; + return ($num / $divisor); + }; + if ($opts{verbose}) { + printf " %02s: %-8s (pct ) %-10s (pct ) %-6s (pct ) get_hits (pct ) cmd_set (pct )\n", + 'sb', 'evicted', 'items', 'pages'; + for my $slab (@$sorted) { + printf " %02d: %-8d (%.2f%%) %-10s (%.4f%%) %-6d (%.2f%%) %-8d (%.3f%%) %-7d (%.2f%%)\n", + $slab->{slab}, $slab->{evicted_d}, + $pct->($slab->{evicted_d}, $totals->{evicted_d}), + $slab->{number}, + $pct->($slab->{number}, $totals->{number}), + $slab->{total_pages}, + $pct->($slab->{total_pages}, $totals->{total_pages}), + $slab->{get_hits_d}, + $pct->($slab->{get_hits_d}, $totals->{get_hits_d}), + $slab->{cmd_set_d}, + $pct->($slab->{cmd_set_d}, $totals->{cmd_set_d}); + } + } + + next unless @$sorted; + my $highest = $sorted->[-1]; + $stats{$highest->{slab}}++; + print " (winner: ", $highest->{slab}, " wins: ", $stats{$highest->{slab}}, ")\n"; + automove_basic($totals, $sorted) if ($opts{automove}); + + $slabs_before = $slabs_after; + } +} + +sub grab_stats { + my %slabs = (); + for my $stat (qw/items slabs/) { + print $sock "stats $stat\r\n"; + while (my $line = <$sock>) { + chomp $line; + last if ($line =~ m/^END/); + if ($line =~ m/^STAT (?:items:)?(\d+):(\S+) (\S+)/) { + my ($slab, $var, $val) = ($1, $2, $3); + $slabs{$slab}->{$var} = $val; + } + } + } + + return \%slabs; +} + +# Really stupid algo, same as the initial algo built into memcached. +# If a slab "wins" most evictions 3 times in a row, pick from a slab which +# has had 0 evictions 3 times in a row and move it over. +sub automove_basic { + my ($totals, $sorted) = @_; + + my $source = 0; + my $dest = 0; + my $high = $sorted->[-1]; + return unless $high->{evicted_d} > 0; + if ($move{winner} == $high->{slab}) { + $move{wins}++; + $dest = $move{winner} if $move{wins} >= $opts{loops}; + } else { + $move{wins} = 1; + $move{winner} = $high->{slab}; + } + for my $slab (@$sorted) { + my $id = $slab->{slab}; + if ($slab->{evicted_d} == 0 && $slab->{total_pages} > 2) { + $move{zeroes}->{$id}++; + $source = $id if (!$source && $move{zeroes}->{$id} >= $opts{loops}); + } else { + delete $move{zeroes}->{$slab->{slab}} + if exists $move{zeroes}->{$slab->{slab}}; + } + } + + if ($source && $dest) { + print " slabs reassign $source $dest\n"; + print $sock "slabs reassign $source $dest\r\n"; + my $res = <$sock>; + print " RES: ", $res; + } elsif ($dest && !$source) { + print "FAIL: want to move memory to $dest but no valid source slab available\n"; + } +} + +# Using just the evicted stats. +sub calc_results_evicted { + my ($slabs, $totals) = calc_slabs(@_); + my @sorted = sort { $a->{evicted_d} <=> $b->{evicted_d} } values %$slabs; + return ($totals, \@sorted); +} + +# Weighted ratios of evictions vs total stored items +# Seems to fail as an experiment, but it tries to weight stats. +# In this case evictions in underused classes tend to get vastly inflated +sub calc_results_numratio { + my ($slabs, $totals) = calc_slabs(@_, sub { + my ($sb, $sa, $s) = @_; + if ($s->{evicted_d}) { + $s->{numratio} = $s->{evicted_d} / $s->{number}; + } else { $s->{numratio} = 0; } + }); + my @sorted = sort { $a->{numratio} <=> $b->{numratio} } values %$slabs; + return ($totals, \@sorted); +} + +sub calc_slabs { + my ($slabs_before, $slabs_after, $code) = @_; + my %slabs = (); + my %totals = (); + for my $id (keys %$slabs_after) { + my $sb = $slabs_before->{$id}; + my $sa = $slabs_after->{$id}; + next unless ($sb && $sa); + my %slab = %$sa; + for my $key (keys %slab) { + # Add totals, diffs + if ($slab{$key} =~ m/^\d+$/) { + $totals{$key} += $slab{$key}; + $slab{$key . '_d'} = $sa->{$key} - $sb->{$key}; + $totals{$key . '_d'} += $sa->{$key} - $sb->{$key}; + } + } + # External code + $code->($sb, $sa, \%slab) if $code; + $slab{slab} = $id; + $slabs{$id} = \%slab; + } + return (\%slabs, \%totals); +} |