parallel I/O on shared-memory multi-CPU machines

Larry McVoy lm at
Tue Apr 3 22:53:36 UTC 2007

On Tue, Apr 03, 2007 at 03:50:27PM -0700, David Schwartz wrote:
> > I write scientific number-crunching codes which deal with large
> > input and output files (Gb, tens of Gb, as much as hundreds of
> > Gygabytes on occasions). Now there are these multi-core setups
> > like Intel Core 2 Duo becoming available at a low cost. Disk I/O
> > is one of the biggest bottlenecks. I would very much like to put
> > to use the multiple processors to read or write in parallel
> > (probably using OMP directives in a C program).
> How do you think more processors is going to help? Disk I/O doesn't take
> much processor. It's hard to imagine a realistic disk I/O application that
> was somehow limited by available CPU.

Indeed.  S/he is mistaking CPUs for DMA engines.  The way you make this go
fast is a lot of disk controllers running parallel.  A single CPU can
handle a boatload of interrupts.
Larry McVoy                lm at 

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