#!/usr/bin/perl

# calculcate average latency

use Linux::AIO;
use Time::HiRes qw(time);
use File::Glob qw();

my $START = time;
my $SELECT;

for(File::Glob::glob "/fs/anime/eps/*Basara/*") {
   my $fh;
   print "$_\n";
   open $fh, "<", $_ or die "$_: $!";
   push @fh, $fh;
}

Linux::AIO::min_parallel 50;
$nreqs = 50;

my $lat;
my $cnt = 1e-36;

$|=1;

sub gen_request {
   my $fh = @fh[rand @fh];
   my $offset = int rand 75000000;
   my $data;
   my $start = time;
   #print "starting new req ($fh, $offset)\n";
   aio_read($fh, $offset, 8192, $data, 0, sub {
      $start = time - $start;
      $lat += $start;
      $cnt++;
      #print "io returned ($fh, $offset, $start)\n";
   });
}

gen_request while (Linux::AIO::nreqs < $nreqs);

my $sr = ""; vec($sr, Linux::AIO::poll_fileno, 1) = 1;

while(1) {
   if (Linux::AIO::nreqs < $nreqs) {
      gen_request;
   } else {
      $SELECT -= time;
      my $r;
      select $r = $sr, undef, undef, undef;
      $SELECT += time;
   }
   Linux::AIO::poll_cb;
   printf "\r$lat $cnt %.2f %.3f   ", $lat / $cnt, $SELECT/(time - $START);
}