Re: efficient access to "rotational"; new fcntl?

[Avi Kivity]

On 09/19/2009 12:19 PM, Arjan van de Ven wrote:
> > However, sort *would* benefit, and some UCLA students implemented that
> > for a term project.  Unfortunately, the project is stalled because the
> > implementation was not efficient enough, and no one has found the
> > time to improve it since.
> >      
> parallel sort... call me skeptical. My gut feeling is that you'll get
> killed by communication overhead.
> (sort seems to be more communication than raw cpu use)
>
>    

Why?  a sort that fits in memory is purely cpu and memory access.

Instead of O(N log N) you'd get K * O(N/K log N/K) followed by an O(N) 
merge.  For large N and small K, you get a speedup of roughly K (since 
the O(N) merge is dominated by the preceding sort.


--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/