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Fix to replace vmstat with /proc sampler for same output with much lower overhead

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This commit is contained in:
Ilia Ross
2025-10-01 18:35:20 +03:00
parent a4d1280ef7
commit e6e79a7eb5
2 changed files with 58 additions and 23 deletions
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1
CHANGELOG.md
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@@ -6,6 +6,7 @@
* Fix the printing of the bottom button row in the form column table
* Fix to recommend Perl `Sys::Syslog` module #2557
* Fix to avoid using short hostname in HTTPS redirects when an FQDN is available
* Fix to use _/proc_ sampler instead of `vmstat` for the same output with much lower overhead
* Fix to query specific fields in FreeBSD memory stats collection, cutting CPU use by 80%
* Add a complete overhaul of `var_dump` subroutine, which is now fully portable
* Update the Authentic theme to the latest version with various fixes:

80
proc/linux-lib.pl
View File

@@ -754,31 +754,65 @@ return (\@cpu, \@fans);
}
# get_cpu_io_usage()
# Returns a list containing CPU user, kernel, idle, io and VM time, and IO
# blocks in and out
# Returns a list of "us", "sy", "id", "wa", "st", "bi", "bo" that match `vmstat`
# output by using /proc with much lower overhead
sub get_cpu_io_usage
{
my ($nodelay) = @_;
my $interval;
$interval = " 1 2"
if (!$nodelay);
my ($out, @lines, @w);
if (&has_command("vmstat")) {
$out = &backquote_command("vmstat$interval 2>/dev/null");
@lines = split(/\r?\n/, $out);
@w = split(/\s+/, $lines[$#lines]);
shift(@w) if ($w[0] eq '');
if ($w[8] =~ /^\d+$/ && $w[9] =~ /^\d+$/) {
return ( @w[12..16], $w[8], $w[9] );
}
} elsif (&has_command("dstat")) {
$out = &backquote_command("dstat 1 1 2>/dev/null");
@lines = split(/\r?\n/, $out);
@w = split(/[\s|]+/, $lines[$#lines]);
shift(@w) if ($w[0] eq '');
return( @w[0..4], @w[6..7]);
}
return undef;
# Read CPU counters from /proc/stat, the first "cpu" line
my $read_cpu = sub {
open(my $fh, '<', '/proc/stat') or return;
my $line = <$fh>;
close($fh);
return unless defined $line && $line =~ /^cpu\s+/;
my @v = split /\s+/, $line; shift @v;
push @v, (0) x (8-@v) if @v < 8;
return @v[0..7];
};
# Read pgpgin/pgpgout from /proc/vmstat (in KB). Note, that all modern kernels,
# /proc/vmstat pgpgin/pgpgout are KiB (scale=1); not as *pages*, so no need to
# convert deltas
my $read_io = sub {
open(my $fh, '<', '/proc/vmstat') or return (undef, undef);
my ($in, $out);
while (my $l = <$fh>) {
$in = $1 if !defined $in && $l =~ /^pgpgin\s+(\d+)/;
$out = $1 if !defined $out && $l =~ /^pgpgout\s+(\d+)/;
last if defined $in && defined $out;
}
close($fh);
return ($in, $out); # KB on kernels 2.6.18+; no conversion needed
};
# Sample A
my @cb = $read_cpu->() or return;
my ($pgin_b, $pgout_b) = $read_io->();
# Sleep half a second
select(undef, undef, undef, 0.5);
# Sample B
my @ca = $read_cpu->() or return;
my ($pgin_a, $pgout_a) = $read_io->();
# CPU percentages as in vmstat
my @d = map { $ca[$_] - $cb[$_] } 0..7;
for (@d) { $_ = 0 if $_ < 0 }
my $tot = 0; $tot += $_ for @d[0..7];
return if !$tot;
# Calculate percentages
my $us = int( (($d[0] + $d[1]) / $tot) * 100 ); # user+nice
my $sy = int( (($d[2] + $d[5] + $d[6]) / $tot) * 100 ); # system+irq+softirq
my $id = int( ( $d[3] / $tot ) * 100 ); # idle
my $wa = int( ( $d[4] / $tot ) * 100 ); # iowait
my $st = int( ( $d[7] / $tot ) * 100 ); # steal
# Calculate bi/bo in KiB/s over half a second
my ($bi, $bo) = (0, 0);
$bi = int( (($pgin_a // 0) - ($pgin_b // 0)) / 0.5 );
$bo = int( (($pgout_a // 0) - ($pgout_b // 0)) / 0.5 );
return ($us, $sy, $id, $wa, $st, $bi, $bo);
}
# has_disk_stats()