add naive sysread / read benchmark

tools/benchmarks/read_vs_sysread.pl

@@ -0,0 +1,65 @@
+use 5.18.1;
+
+use Time::HiRes qw(gettimeofday tv_interval);
+
+my $total_bytes = 5_000_000;
+my @lengths = (1, 2, 3, 4, 10, 50, 100, 1_000, 10_000);
+
+foreach my $length (@lengths) {
+
+    my $packet_nb = int($total_bytes / $length);
+    my %results;
+
+    my $method = "read";
+    if (my $pid = open(my $kid, "|-")) {
+        # parent
+        my $data = 'x' x $length;
+        my $i = $packet_nb;
+        my $t0 = [gettimeofday];
+        while ($i--) {
+            print $kid $data;
+        }
+        close($kid) or warn "kid exited with $?";
+        my $elapsed = tv_interval ($t0); # equivalent code
+        say "$method: $packet_nb packets of size $length : $elapsed sec";
+        $results{$method}{$length} = $elapsed;
+    } else {
+        # child
+        my $data;
+        my $i = 0;
+        while ($i < $packet_nb) {
+            read STDIN, $data, $length, $i*$length;
+            $i++;
+        }
+        length($data) eq $length * $packet_nb
+          or say "wrong length : got " . length($data) . " instead of " . $length * $packet_nb;
+        exit;  # don't forget this
+    }
+
+    my $method = "sysread";
+    if (my $pid = open(my $kid, "|-")) {
+        # parent
+        my $data = 'x' x $length;
+        my $i = $packet_nb;
+        my $t0 = [gettimeofday];
+        while ($i--) {
+            syswrite $kid, $data, $length;
+        }
+        close($kid) or warn "kid exited with $?";
+        my $elapsed = tv_interval ($t0); # equivalent code
+        say "$method: $packet_nb packets of size $length : $elapsed sec";
+        $results{$method}{$length} = $elapsed;
+    } else {
+        # child
+        my $data;
+        my $i = 0;
+        while ($i < $packet_nb) {
+            sysread STDIN, $data, $length, $i*$length;
+            $i++;
+        }
+        length($data) eq $length * $packet_nb
+          or say "wrong length : got " . length($data) . " instead of " . $length * $packet_nb;
+        exit;  # don't forget this
+    }
+
+}