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SubjectRe: (disk/cpu) kernel performance problem
> 45% is the amount of time the kernel spends in loading data from disk.

no, 45 is a nearly arbitrary number that the kernel gives you. it's trivial
to demonstrate examples that show the number to be unrelated to real %CPU.


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

no, you believe the number too much. it's an idiot gauge, a blinkenlight.
to make a more reasonable measurement of CPU overhead of IO, run a
compute-bound thread, and watch it change during IO and not. naturally,
you'll need to deal with the fact that there are numerous kinds of
cost to IO.

finally, zero copying is not Linux's (Linus's) stated goal, for quite
rational reasons.

regards, mark hahn.


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