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Status Delivered
Workspace Informix
Components Informix Server
Created by Guest
Created on May 7, 2019

Informix AIO tunig options in the way kernel resources are allocated (aio-nr).

When you bring up a instance of the Informix Server which uses KAIO the instance goes out and takes 50% of the aio-nr resources from what I have been able find.   then when a second instance comes up it took like 75% of the resources left and then a 3rd Instance take instance takes 10% of what is left and the 4th takes 3%. and so on.


It seems to take the aio-max-nr and subtract the value of aio-nr and takes x% of what is available.


the one issue is if you run out you can bump the aio-max-nr dynamically but it takes 50% of the resources with the 1st instance so if you start with the kernel minimum of 65536 the ist instance takes 32,762 of that or if you set to 250,000 it takes 125,000.


What I have actually found works but not nice is to set it say to 100,000 bring up 1st instance then dynamically bump the aio-max-nr to 225,000 and bring up second instance and continue bumping the value.


I have also seen recommendationsof setting this to 1-2 million but as it works with a % of the difference where do you stop at some point you may have issues.  at 65536 I was able to bring up 3 safely but then you have no growth in the aio resources.

  • Admin
    Karen Qualley
    Sep 12, 2019

    Available in 14.10.xc2

  • Guest
    Jul 1, 2019

    As per machine notes this is already available "

    The number of requests allocated per CPU VP can be controlled by
        the environment variable KAIOON, by setting it to the required value before
        starting the server.