libevent and epoll

[Brad Fitzpatrick]

Perrin,

I tuned Memcached's Perl library, removing the dependence on the slow
IO::Socket library.  Checking it into CVS now.

Memcached is now twice as fast (wall clock) as your unrealistic DBD
benchmark:


bradfitz@apfel:~/benchmark$ ./bench.pl
Benchmark: timing 100 iterations of DBD::mysql, MemCachedClient...
DBD::mysql: 24 wallclock secs ( 6.34 usr +  3.06 sys =  9.40 CPU) @ 10.64/s (n=100)
MemCachedClient: 11 wallclock secs ( 5.90 usr +  1.78 sys =  7.68 CPU) @ 13.02/s (n=100)
                  Rate      DBD::mysql MemCachedClient
DBD::mysql      10.6/s              --            -18%
MemCachedClient 13.0/s             22%              --


What are you doing all this benchmark work for, anyway?

- Brad


On Sun, 28 Sep 2003, Perrin Harkins wrote:

> On Tue, 2003-09-23 at 00:28, Brad Fitzpatrick wrote:
> > And use our binary, which is built with a libevent with epoll support,
> > including epoll bugfixes which aren't in 0.7a (the latest libevent version
> > on the site).
> >
> > http://www.danga.com/memcached/dist/binaries/linux-x86/memcached-1.1.9-snapshot-dbg.gz
> >
> > Test it with:
> >
> > $ EVENT_SHOW_METHOD=1 ./memcached
> >
> > It should say "Using: epoll" or similar.
>
> Thanks for the help.  I got this working (on linux kernel 2.4.21), but
> I'm getting pretty poor performance so I think I must have a mistake in
> my code somewhere.  At the moment, MySQL, IPC::MM, and BerkeleyDB are
> all much faster than memcached in my tests.
>
> I'm starting the server with this command:
>
> ./memcached-1.1.9-snapshot-dbg -d -m 128 -l 127.0.0.1 -p 11211
>
> Here's the client code I use.  IPC::SharedHash is an asbtraction layer
> that allows me to test all forms of storage with the same API.
>
> package IPC::SharedHash::MemCachedClient;
>
> use strict;
> use warnings;
>
> use MemCachedClient;
>
> sub new {
>     my $class   = shift;
>     my $self    = {};
>     my $memc    = MemCachedClient->new(
>         {
>             'servers'            => ['127.0.0.1:11211'],
>             'debug'              => 0,
>             'compress_threshold' => 10_000,
>         }
>     );
>
>     $self->{'backend'} = $memc;
>     bless $self, $class;
>     return $self;
> }
>
> sub fetch {
>     my $self  = shift;
>     my ($key) = @_;
>     my $value = $self->{'backend'}->get($key);
>     return $value;
> }
>
> sub store {
>     my $self = shift;
>     my ( $key, $value ) = @_;
>     $self->{'backend'}->set( $key, $value );
> }
>
> 1;
>
> Does anyone see any problems here?  By the way, lines 305 and 306 of the
> Perl client API were giving warnings, but neither turning off warnings
> nor fixing the problem made a significant difference to performance.
> Here's the output of my benchmark script:
>
>                   Rate MemCachedClient      DBD::mysql         IPC::MM
> MemCachedClient 16.4/s              --            -53%            -85%
> DBD::mysql      35.0/s            114%              --            -68%
> IPC::MM          109/s            564%            210%              --
>
> - Perrin
>
>