Re: Why don't have bits the same rights as humans! (flushing to disk waiting time)

[Daniel Phillips <phillips@bonn-fries.net>]

On August 19, 2001 11:11 pm, Otto Wyss wrote:
> I recently wrote some small files to the floppy disk and noticed almost nothing
> happened immediately but after a certain time the floppy actually started
> writing. So this action took more than 30 seconds instead just a few. This
> remembered me of the elevator problem in the kernel. To transfer this example
> into real live: A person who wants to take the elevator has to wait 8 hours
> before the elevator even starts. While probably everyone agrees this is
> ridiculous in real live astonishingly nobody complains about it in case of a disk.

My early flush patch, posted a month or so ago, takes care of this nicely.
I'm just waiting for 2.5 to roll around to do some more work on it.

> [...]
> Could anybody produce any real figures to prove/disprove my theory? Could
> anybody benchmark the disk access for the 3 waiting times (0, 200ms 30sec) with
> different loads?

Your theory is correct.  I implemented the idea, took measurements, and found
dramatic performance improvements under some loads, while getting worse on
none.  You can search lwn.net for a nice writeup by Jonathan Corbett.

--
Daniel