Re: An elevator algorithm (patch)

[Andrea Arcangeli]

On Tue, Sep 19, 2000 at 07:17:42AM -0300, Rik van Riel wrote:
> This is a bug in Andrea's idea.  The request should only
> be inserted at the end of the list if:
> 
> 1) the block numbre is bigger than head->prev (which you
>    already have)

If you read the code you'll see that in his previous patch he wasn't doing
that.  That's what I suggested to change to return in O(1) behaviour.

> 2) the block number is smaller than head (or head->next
>    if the current request is unplugged)

You're wrong. While the queue is unplugged there are peaks in the queue caused
by the latency control and head->next is not guarnateed to be the lower block
in the queue.

Andrea
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