[opensuse] Re: user/sys ticks for process exceed overall user/sys ticks

1 Mar 2014


      Linda Walsh wrote:
...
Peter Hofer wrote:
...
...
./ticks.py 
delta process: user: 2495 sys: 181
delta all: user: 2283 sys: 258

Despite the confusion regarding ticks vs. jiffies, 
I was curious what the same program woudl do in perl...
...
time python ticks.py
    delta process: user: 9263 sys: 2987
    delta all: user: 6034 sys: 2178
67.35sec 92.64usr 29.89sys (181.94% cpu)
...
time perl /tmp/pticks
    delta process: user: 2917  sys: 3
    delta all: user: 2926  sys:  25
3.36sec 29.20usr 0.03sys (870.05% cpu)
---
!!!  The perl version is 20x faster as it uses the multiple cores.
For 9 threads:
lang    #thrds  #coresuse  %efficency
----    ------    ------     -------
python    9        1.82       20.2%
perl      9        8.70       96.7%
(2 CPU's @ 6 cores ea @ 1.6-2.8GHz using on-demand scheduler).
Source attached.  I tried to use as close to same semantics
as the python program.  Even used python indentation where
practical (I did split the prints at the end... something
python seems to have problems with...)
#!/usr/bin/perl
use 5.16.0;
use threads;
use P;

sub open_for_read($) {
	open(my $handle, "<$_[0]") or die "opening $_[0]: $!";
	$handle }

sub ticks_all {
	my $f = open_for_read("/proc/stat");
	return (split ' ', <$f>)[1,3] }

sub ticks_process() {
	my $f = open_for_read("/proc/self/stat");
	return (split ' ', <$f>)[13,14] }

sub dowork () {
	use Digest::MD5;
	my $d = Digest::MD5->new;
	$d->add('nobody inspects');
	$d->add(' the spammish repetition') for (0 .. 10_000_000)} 

my ($before_all_user, $before_all_sys) = ticks_all();
my ($before_process_user, $before_process_sys) = ticks_process();

my @threads; 
for my $i (0 .. 8) {
	my $t = threads->create(\&dowork);
	push @threads,$t }
$_->join() foreach @threads;

my ($after_all_user, $after_all_sys) = ticks_all();
my ($after_process_user, $after_process_sys) = ticks_process();

#(note: changing perl defaults for print)
$, = " ";   #put spaces between output fields
$\ = "\n";	#add LF to end of lines by default

print 'delta process: user:', $after_process_user - $before_process_user, 
			' sys:', $after_process_sys - $before_process_sys;
print 'delta all: user:', $after_all_user - $before_all_user, 
			' sys: ', $after_all_sys - $before_all_sys;