Re: Perl Quiz of the Week #23

[email protected] (Kurt Starsinic):
>     % time parens 12 > /dev/null
>     real    0m4.541s
>     user    0m4.460s
>     sys     0m0.012s
> 
>     The "tail" version has to generate all the output, it just doesn't
> have to display most of it to the s*l*o*w tty.  Interestingly, the
> "/dev/null" version isn't that much faster, which reinfoces the idea
> that the slowness isn't in the I/O subsystem per se, but rather in the
> tty driver specifically.

I don't think the > /dev/null version is using the TTY driver.  Why
would it be?

The data *does* have to be copied into the kernel buffer.  But from
there the kernel invokes the device driver, which in this case returns
immediately.

I guess that you will not see much decrease in time if you remove the
printing from your program.