Virtual machine I/O interrupt control method compares number of pending I/O interrupt conditions for non-running virtual machines with predetermined number

A method of operating a computer having at least a central processing unit (CPU), main storage, channels and input/output devices connected to the main storage through the channels, comprising the steps of:

• configuring said computer to run a plurality of operating systems including generating a logical partition (LPAR) for each said operating system and exclusively allocating hardware resources of said computer to each said LPAR on a time sharing basis under control of a virtual machine control program;
• sending input/output instructions to a plurality of said devices through a plurality of said channels and unsynchronously receiving corresponding input/output interrupt conditions through the channels;
• controlling acknowledging of said input/output interrupt conditions for a dispatched LPAR so that only input/output interrupt conditions corresponding to said dispatched LPAR are acknowledged;
• recognizing and holding the input/output interrupt conditions in a pending state for each of said LPARs other than a dispatched one of said LPARs;
• registering data of counts of each of said pending input/output interrupt conditions for each of said LPARs other than a dispatched one of said LPARs and comparing each of said counts to a predetermined threshold number;
• suspending running of the operating system of a dispatched LPAR when one of said counts for a corresponding said LPAR exceeds said threshold number including returning control of said computer to said virtual machine control program;
• reading said registered data of counts and determining from said registered data of counts which of said LPARs is to be dispatched next;
• dispatching said next to be dispatched LPAR;
• and
• said dispatching including dispatching each said LPAR with a start interpretive execution command having an operand specifying said threshold number, and registering said threshold number with said virtual machine control program for a dispatched LPAR.

A method of operating a plurality of virtual machines running on a computer having a central processing unit (CPU), comprising the steps of:

• generating a logical partition (LPAR) for each of said virtual machines and allocating hardware resources on a time-sharing basis to each of said LPARs, including exclusive devices and channels for each of said LPARs, each said LPAR initialing input/output operations and receiving input/output interrupt responses through said channels;
• controlling dispatching of each of said LPARs with a virtual machine control program that dispatches one of said LPARs at a time;
• after one said LPAR has been dispatched by said virtual machine control program, acknowledging input/output interrupts for only said dispatched LPAR and said virtual machine control program, and holding input/output interrupt conditions pending for each of said LPARs other than said dispatched LPAR;
• counting an occurrence of each of said pending input/output interrupt conditions for each of said LPARs other than said dispatched LPAR to obtain a count and comparing said count to a predetermined threshold number;
• continuing said holding when said count is equal to or less than said threshold number;
• suspending running of said dispatched LPAR and returning control or said computer to said virtual machine control program when said count exceeds said threshold number;
• selecting a next to be dispatched one of said LPARs and dispatching said selected LPAR with said virtual machine program;
• wherein said selecting step includes determining which of said LPARs has a greatest number of pending input/output interrupt conditions and selecting said LPAR with said greatest number of pending input/output interrupt conditions as said next to be dispatched LPAR;
• and
• wherein said dispatching includes dispatching each said LPAR with a start interpretive execution command having an operand specifying said threshold number, and registering said threshold number with said virtual machine control program for a dispatched LPAR.