From: Clifford Heath <cjh_nospam@...>
Date: 2002-06-21T13:48:52+09:00
Subject: Re: Why is I/O slow?

Clifford Heath wrote:
> Anyhow, thanks to Radek for the advice, I've got 1.6.7 and the performance
> of sysread seems comparable to read now.

Sorry, must have tested the wrong version somehow - read is still slow.

$ time ruby cat_read.rb  /tmp/ten_megabytes  > /dev/null
real    0m1.259s
user    0m1.210s
sys     0m0.050s
$ time ruby cat_sysread.rb  /tmp/ten_megabytes  > /dev/null
real    0m0.148s
user    0m0.080s
sys     0m0.060s

One thing I don't get: my C program takes 65ms, but Perl
and /bin/cat take only 35ms. Perl and C programs follow.
BTW a larger buffer than 65K slows both down - cache size.

# cat.pl
my $buf;
my $r;
while (sysread(STDIN, $buf, 65536) > 0)
{
        print $buf
}

main()
{
        int     r;
        char    buf[65536];

        while ((r = read(0, buf, sizeof(buf))) > 0)
                write(1, buf, r);
}

Thoughts?

--
Clifford Heath