Re: elevator algorithm bug in ll_rw_blk.c

Tim Smith (tzs@tzs.net)
Mon, 16 Nov 1998 09:23:08 -0800 (PST)


On 16 Nov 1998, H. Peter Anvin wrote:
> Do you really want to bother keeping track of them, especially since
> modern drives have different numbers of sectors per track?

I'm not suggesting that all of that information should be used. I was
just responding to the post that said it wasn't determinable on modern
drives. We *can* get pretty much all the information to implement any
fancy scheduling algorithm, at the cost of perhaps a few hours of probing
the disk at formating time. Whether that is a good idea or not I am not
qualified to judge.

> I think the current algorithm (a) works well, (b) avoids penalizing
> part of the disk, and (c) is simple.

Rotational optimization might be worthwhile. On many modern drives, the
rotational latency is larger than the seek latency for requests that
aren't a large number of cylinders apart.

--Tim Smith

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