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Full Discussion: IO performance symptoms
Special Forums Hardware Filesystems, Disks and Memory IO performance symptoms Post 302345254 by zxmaus on Tuesday 18th of August 2009 06:23:19 PM
Old 08-18-2009

disks are only thrashing when you are very low in memory and your systems is permanently paging in and out.

Disks being busy up to 70% is normal on AIX and no reason for concern ... are you trying to investigate high IO waits from cpu? What kind of applications do you run?

I agree with DukeNuke, it would be more helpful if we could see your stats to tell you more than fishing in the dark.


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dispatch_benchmark(3)					   BSD Library Functions Manual 				     dispatch_benchmark(3)

dispatch_benchmark -- Measures block execution time SYNOPSIS
#include <dispatch/dispatch.h> uint64_t dispatch_benchmark(size_t count, void (^block)(void)); uint64_t dispatch_benchmark_f(size_t count, void *context, void (*function)(void *)); DESCRIPTION
The dispatch_benchmark() function executes the given block multiple times according to the count variable and then returns the average number of nanoseconds per execution. This function is for debugging and performance analysis work. For the best results, pass a high count value to dispatch_benchmark(). When benchmarking concurrent code, please compare the serial version of the code against the concurrent version, and compare the concurrent version on different classes of hardware. Please look for inflection points with various data sets and keep the following facts in mind: o Code bound by computational bandwidth may be inferred by proportional changes in performance as concurrency is increased. o Code bound by memory bandwidth may be inferred by negligible changes in performance as concurrency is increased. o Code bound by critical sections may be inferred by retrograde changes in performance as concurrency is increased. o Intentional: locks, mutexes, and condition variables. o Accidental: unrelated and frequently modified data on the same cache-line. RETURN VALUE
The dispatch_benchmark() function returns the average number of nanoseconds the given block takes to execute. SEE ALSO
dispatch(3) Darwin May 1, 2009 Darwin

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