Messages in this thread | | | Date | Tue, 27 Jul 1999 10:32:55 -0400 | From | Mark Lord <> | Subject | Re: (disk/cpu) kernel performance problem |
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Gerald Aigner wrote: .. > > 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.
Okay, So install a *slower* disk, and you'll see that number drop dramatically, to perhaps 15-20%. That is because the overall elapsed time will increase, "reducing" the percentage of CPU spent doing I/O, even though the total CPU utilization for I/O remains unchanged (and quite small). Get it now? -- mlord@pobox.com
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