Hello,
Need advice why shared memory is so slow. My assumption was that shared memory is like usual memory. But this simple test show contrary.
I guess that my test is bad... 
#!/usr/bin/evn perl
use strict;
use warnings;

use Benchmark qw(:all :hireswallclock);
use IPC::SysV qw(IPC_CREAT);
use Data::Dumper::Concise;

my $data;
my $size = 65536;

my $id = shmget('12345', $size, IPC_CREAT | 0666);

my $mem = join('', map { ('a' .. 'z')rand(26) } (1..65536));
open(MEMORY, "<", \$mem);

shmwrite( $id, $mem, 0, $size );

cmpthese( -1, {
    'shmread'     => sub { shmread( $id, $data, 0, $size ) || die "shmread: $!" },
    'memory read' => sub { read( MEMORY, $data, $size, 0 ) // die "read: $!" },
});

$ perl bin/test/bench/shmread.pl 
                  Rate     shmread memory read
shmread        36202/s          --       -100%
memory read 10155128/s      27951%          --

In reply to Slow shared memory issue by bash

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