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Posted to modperl@perl.apache.org by Barrie Slaymaker <ba...@slaysys.com> on 2000/06/08 18:09:08 UTC
Method overhead benchmarks [Was: [performance/benchmark] printing
techniques]
Stephen Zander wrote:
>
> As Matt has already commented, in the handler the method call
> overheads swamps all the other activities.
Just to clarify: that's only important if you are doing very few other
activities, or if those other activities also include a high percentage
of method calls:
###### Using an empty A::a() (see below):
Benchmark: running $a->a(), A->a(), A::a( "A" ), A::a( $a ), A::a(), a(), each for at least 3 CPU seconds...
$a->a(): 4 wallclock secs ( 3.24 usr + 0.02 sys = 3.26 CPU) @ 511465.64/s (n=1667378)
A->a(): 2 wallclock secs ( 3.28 usr + 0.00 sys = 3.28 CPU) @ 290696.34/s (n=953484)
A::a( "A" ): 3 wallclock secs ( 3.08 usr + 0.00 sys = 3.08 CPU) @ 610704.55/s (n=1880970)
A::a( $a ): 3 wallclock secs ( 3.07 usr + 0.00 sys = 3.07 CPU) @ 623101.63/s (n=1912922)
A::a(): 3 wallclock secs ( 3.22 usr + 0.00 sys = 3.22 CPU) @ 611970.19/s (n=1970544)
a(): 3 wallclock secs ( 3.14 usr + 0.00 sys = 3.14 CPU) @ 622945.22/s (n=1956048)
Rate A->a() $a->a() A::a( "A" ) A::a() a() A::a( $a )
A->a() 290696/s -- -43% -52% -52% -53% -53%
$a->a() 511466/s 76% -- -16% -16% -18% -18%
A::a( "A" ) 610705/s 110% 19% -- -0% -2% -2%
A::a() 611970/s 111% 20% 0% -- -2% -2%
a() 622945/s 114% 22% 2% 2% -- -0%
A::a( $a ) 623102/s 114% 22% 2% 2% 0% --
###### And doing some trivial work in A::a():
[barries@jester tmp]$ perl ./cmp2
Name "A::b" used only once: possible typo at ./cmp2 line 7.
Benchmark: running $a->a(), A->a(), A::a( "A" ), A::a( $a ), a(), each for at least 3 CPU seconds...
$a->a(): 5 wallclock secs ( 3.19 usr + 0.00 sys = 3.19 CPU) @ 64346.39/s (n=205265)
A->a(): 4 wallclock secs ( 3.21 usr + 0.00 sys = 3.21 CPU) @ 54105.30/s (n=173678)
A::a( "A" ): 2 wallclock secs ( 3.09 usr + 0.00 sys = 3.09 CPU) @ 70333.66/s (n=217331)
A::a( $a ): 3 wallclock secs ( 3.19 usr + 0.00 sys = 3.19 CPU) @ 68128.84/s (n=217331)
a(): 4 wallclock secs ( 3.10 usr + 0.00 sys = 3.10 CPU) @ 72231.29/s (n=223917)
Rate A->a() $a->a() A::a( $a ) A::a( "A" ) a()
A->a() 54105/s -- -16% -21% -23% -25%
$a->a() 64346/s 19% -- -6% -9% -11%
A::a( $a ) 68129/s 26% 6% -- -3% -6%
A::a( "A" ) 70334/s 30% 9% 3% -- -3%
a() 72231/s 34% 12% 6% 3% --
You can see that even doing a few things in A::a() cause the relative slowdown
due to method call overhead to drop significantly. I suspect that your opcode
count has more to do with it than method overhead, unless I've goofed the
benchmarks somehow.
Hmmm, maybe this shows it best (though I did tweak aggrlist_print to
print STDERR):
[barries@jester tmp]$ perl ./aggr_cmp 2> /dev/null
Benchmark: running $a->aggrlist_print(), A->aggrlist_print(), aggrlist_print( $a ), each for at least 3 CPU seconds...
$a->aggrlist_print(): 3 wallclock secs ( 2.69 usr + 0.41 sys = 3.10 CPU) @ 15104.19/s (n=46823)
A->aggrlist_print(): 3 wallclock secs ( 2.72 usr + 0.41 sys = 3.13 CPU) @ 14492.01/s (n=45360)
aggrlist_print( $a ): 3 wallclock secs ( 2.81 usr + 0.24 sys = 3.05 CPU) @ 15529.18/s (n=47364)
Rate A->aggrlist_print() $a->aggrlist_print() aggrlist_print( $a )
A->aggrlist_print() 14492/s -- -4% -7%
$a->aggrlist_print() 15104/s 4% -- -3%
aggrlist_print( $a ) 15529/s 7% 3% --
- Barrie
[barries@jester tmp]$ cat cmp
#!/usr/local/bin/perl -w
## cmp
package A ;
use Benchmark qw( cmpthese ) ;
sub a {}
my $a = bless {}, 'A' ;
cmpthese( -3, {
'a()' => sub { a() },
'A::a()' => sub { A::a() },
'A::a( "A" )' => sub { A::a( "A" ) },
'A::a( $a )' => sub { A::a( $a ) },
'A->a()' => sub { A->a() },
'$a->a()' => sub { $a->a() },
} ) ;
[barries@jester tmp]$ cat cmp2
#!/usr/local/bin/perl -w
## cmp2
package A ;
$b = {} ;
sub a {
my $self = shift ;
my ( $a, $b, $c ) = @_ ;
$b->{FOO} = 'bar' ;
}
use Benchmark qw( cmpthese ) ;
my $a = bless {}, 'A' ;
cmpthese( -3, {
'a()' => sub { a() },
'A::a( "A" )' => sub { A::a( "A" ) },
'A::a( $a )' => sub { A::a( $a ) },
'A->a()' => sub { A->a() },
'$a->a()' => sub { $a->a() },
} ) ;
[barries@jester tmp]$ cat aggr_cmp
#!/usr/local/bin/perl -w
package A ;
sub aggrlist_print{
my @buffer = ();
push @buffer,"<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML//EN\">\n";
push @buffer,"<HTML>\n";
push @buffer," <HEAD>\n";
push @buffer," <TITLE>\n";
push @buffer," Test page\n";
push @buffer," </TITLE>\n";
push @buffer," </HEAD>\n";
push @buffer," <BODY BGCOLOR=\"black\" TEXT=\"white\">\n";
push @buffer," <H1> \n";
push @buffer," Test page \n";
push @buffer," </H1>\n";
push @buffer," <A HREF=\"foo.html\">foo</A>\n";
push @buffer," <HR>\n";
push @buffer," </BODY>\n";
push @buffer,"</HTML>\n";
print STDERR @buffer;
use Benchmark qw( cmpthese ) ;
my $a = bless {}, 'A' ;
cmpthese( -3, {
'aggrlist_print( $a )' => sub { aggrlist_print( $a ) },
'A->aggrlist_print()' => sub { A->aggrlist_print() },
'$a->aggrlist_print()' => sub { $a->aggrlist_print() },
} ) ;
Re: Method overhead benchmarks [Was: [performance/benchmark]
printingtechniques]
Posted by Barrie Slaymaker <ba...@slaysys.com>.
Matt Sergeant wrote:
>
> You also forgot that print() goes to a tied STDOUT, which is even more of
> an overhead...
Yeah, that'd probably swamp almost all other effects Stas is testing right
there, and it explains Stas's test results when varying $|.
- Barrie
Re: Method overhead benchmarks [Was: [performance/benchmark] printing
techniques]
Posted by Matt Sergeant <ma...@sergeant.org>.
On Thu, 8 Jun 2000, Barrie Slaymaker wrote:
> Stephen Zander wrote:
> >
> > As Matt has already commented, in the handler the method call
> > overheads swamps all the other activities.
>
> Just to clarify: that's only important if you are doing very few other
> activities, or if those other activities also include a high percentage
> of method calls:
You also forgot that print() goes to a tied STDOUT, which is even more of
an overhead...
--
<Matt/>
Fastnet Software Ltd. High Performance Web Specialists
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