Changing tunable values for Asynchronous I/O

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All of the AIO tunables have current, default, minimum and maximum values that can be viewed with the ioo command.

Only the current value of a tunable can be changed with the ioo command. The other three values are fixed and are presented to inform you of the bounds of the tunable. You can change the current value of the tunable anytime and make it persistent for the restart of the operating system. All of the tunables follow the normal rules and options controlled by the ioo command, which is in the performance tool file set.
Nonrestricted tunables are summarized in the following table:
Item Description
minservers Indicates the minimum number of kernel processes per processor dedicated to AIO processing. Because each kernel process uses memory, the minservers tunable value, when multiplied by the number of processors, must not be large when the amount of AIO expected is small. The default value for the minservers tunable is 3.
maxservers Indicates the maximum number of kernel processes per processor that are dedicated to AIO processing. This tunable value, when multiplied by the number of processors, indicates the limit on slow path I/O requests in progress at one time and represents the limit for possible I/O concurrency. The default value for the maxservers tunable is 30.
maxreqs Indicates the maximum number of AIO requests that can be outstanding at one time. The requests include those that are in progress, as well as those that are waiting to be started. The maximum number of AIO requests cannot be less than the value of AIO_MAX, as defined in the /usr/include/sys/limits.h file, but it can be greater. It is appropriate for a system with a high volume of AIO to have a maximum number of AIO requests larger than AIO_MAX. The default value for the maxreqs tunable is 16384.
server_inactivity Indicates a time-out value, in seconds, that causes the server to exit if it is idle (sleeping) without servicing an AIO request. If exiting would cause the total number of servers to fall below minservers * number of CPUs, the server goes back to sleep waiting for an AIO to service. This mechanism helps overall system performance by reducing the number of sleeping processes that are not being used to service AIO requests. The default value for the server_inactivity tunable is 300.