Re: CSCAN vs CFQ I/O scheduler benchmark results

From: Jens Axboe
Date: Mon Jun 12 2006 - 02:39:59 EST



(please don't top post)

On Sun, Jun 11 2006, Vishal Patil wrote:
> Jan
>
> I ran the performance benchmark on an IBM machine with the following
> harddrive attached to it.
>
> cat /proc/ide/hda/model
> ST340014A

Ok, so plain IDE.

> Also note the CSCAN implementation is using rbtrees due which the time
> complexity of the different operations is O(log(n)) and not O(n) and
> that might be the reason that we are getting good values for specially
> in case of sequential writes and the random workloads.

Extremely unlikely. The sort overhead is completely noise in a test such
as yours, an O(n^2) would likely run just as fast.

--
Jens Axboe

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