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SubjectRe: (disk/cpu) kernel performance problem


On Mon, 26 Jul 1999, Mark Lord wrote:

> Gerald Aigner wrote:
> ..
> > Looking into the problem I found that reading large data blocks from
> > two IDE disks with the read(2) library/system call consumes about 45%
> > of the available CPU time when reading roughly 30 Mbytes/sec.
> ...
>
> Percentage of CPU time is not a useful measurement.
> Think about it.. if I/O were infinitely fast, then CPU usage
> would be 100%, since the CPU would never have to wait.
>
> If disk I/O were infinitely slow, CPU usage would be 0%,
> but that's not a Good Thing, is it..
>
45% is the amount of time the kernel spends in loading data from disk.

The lower this value the more time is available for other
threads/applications on the same system therefore increasing overall
system utilization.

-Gerald


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