Re: [RFC] - Some notions that I would like comments on

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Fri, 16 Jul 1999 07:50:23 +0200

Chuck Lever wrote:
> > > I mean, is "readaround" for block @ 128k-192k triggered by
> > > reading/paging within block @ 64k-128k, or is it triggered by the first
> > > read with 128k-192k?
> >
> > No, not yet: it's something which we'll probably do eventually.
> > However, on any vaguely modern hardware, the track buffers on the disk
> > itself will keep filling once you've submitted one IO. Accessing the
> > next cluster will take a latency hit on the CPU, but we still get the
> > full disk bandwidth overall.
>
> why trigger a page-in for the next cluster? doubling the cluster size
> might give the same behavior.

I don't see how it will. Doubling the cluster size just halves the
number of times when we get the latency hit of a synchronous read of the
first page in a cluster.

-- Jamie

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