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Virtual Storage Exerciser (VIRSTOEX or VIRSTOCX)

Virtual Storage Exerciser, an IBM internal tool, is used to create workloads with unique and repeatable storage reference patterns.

The program will run multiple copies on all virtual CPUs available to it. Each loop consists of advancing through guest real storage, starting at 2 GB, reading 8 bytes of data, and optionally changing the 8 bytes of data and then changing the 8 bytes back to their original contents. The program advances the address pointer by the Increment= value and will continue until the address is >= "End Addr", where the End Addr is defined as "Virtual Storage Size - 8". This "normal" processing will be modified if any of the following parameters are specified: AE, AN, AO, AZ, RDpct=, or Wrpct=. If neither Loops= nor Time= is specified, the program will continue indefinitely until interrupted by an external interrupt.

If Go=nnnn is specified, the program will not begin the thrashing phase until at least the specified number of seconds have elapsed since the program was started. This parameter allows coordinated starting of the thrashing phase when the measurement involves multiple concurrent instances of the program.

If Loops= or Time= is specified, the program will terminate when that limit is reached and report the total number of loops done by all Virtual CPUs, the elapsed time, the total number of pages referenced by all Virtual CPUs, and the rate at which pages were referenced.

If any of the "A contrario" options (AE, AN, AO, or AZ) are specified, then the corresponding loops will decrement through virtual storage, beginning with the highest address that would be used in a normal loop and decrementing the address pointer by the Increment= value until the address is <= 2 GB.

If Burnct= is specified, the program will execute the specified number of BrCT instructions after each page is referenced to "burn" additional cycles for each page read and/or changed. The number of cycles actually "burned" is hardware dependent.

If Fwait= is specified, the program will wait a fixed number of milliseconds between loops.

If RWait= is specified, the program will wait a random number of milliseconds (between 0 and the maximum number specified, inclusive) between loops.

If Xwait= is specified, the program will multiply the Fwait= or RWait= value by the Xwait= value for all Virtual CPUs except Virtual CPU 0. The Fwait= or RWait= parameter must also be specified.

If RDpct= is specified, the program will make an initial priming pass to populate storage and build storage management tables. The Increment= value will be used and each page will be read and changed. All other program parameters will be ignored during the priming pass. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program. The program must run in z/CMS mode if RDpct= is specified. On all regular loops, the program will only reference the specified percentage of the total pages in each loop.

If Wrpct= is specified, the program will only change data on that percentage of the total pages being referenced in each loop.

If Stopchk= is specified, the program will perform interim time limit checks during each loop. The time limit will be checked each time the specified number of pages have been read/modified. This will allow more precise control of the program when a loop takes several minutes (e.g. in a 1 TB user). Note that when the program is stopped in this manner, the loop count will be incorrect but the page count, elapsed time, and page rate will be correct.

If Nwait= is specified, the program will wait the specified number of milliseconds when a Stopchk occurs on all Virtual CPUs except Virtual CPU 0. The Stopchk= parameter must also be specified.

If Zwait= is specified, the program will wait the specified number of milliseconds when a Stopchk occurs on Virtual CPU 0. The Stopchk= parameter must also be specified.

If Pprime is specified, the program will make an initial priming pass to build the Page and Segment tables. An increment of 1MB will be used and each page will be read and changed. All other program parameters will be ignored during the priming pass. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program. The program must run in z/CMS mode if Pprime is specified.

If Uprime is specified, the program will make an initial priming pass to build the Upper DAT tables. An increment of 2 GB will be used and each page will be read and changed. All other program parameters will be ignored during the priming pass. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program. The program must run in z/CMS mode if Uprime is specified.

If Vprime= is specified, the program will make an initial priming pass to populate storage and build storage management tables. The specified increment will be used and each page will be read and changed. All other program parameters will be ignored during the priming pass. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program. The program must run in z/CMS mode if Vprime= is specified.

If Querymsg= is specified, the program will write interim progress messages to the console to report the elapsed time, the number of pages referenced, and the rate at which pages were referenced since the last interim progress message. The messages will be written by each Virtual CPU every nnn seconds, as specified by Querymsg= value. The Stopchk= parameter must also be specified.

The following parameters are used to create specific measurement environments.

  • AE - Specifies that all even numbered Virtual CPUs will perform a decrementing (A contrario) address loop, and that all odd numbered Virtual CPUs will perform an incrementing address loop.
  • AN - Specifies that all Virtual CPUs, other than Virtual CPU 0, will perform a decrementing (A contrario) address loop, and that Virtual CPU 0 will perform an incrementing address loop.
  • AO - Specifies that all odd numbered Virtual CPUs will perform a decrementing (A contrario) address loop, and that all even numbered Virtual CPUs will perform an incrementing address loop.
  • AZ - Specifies that Virtual CPU 0 will perform a decrementing (A contrario) address loop, and that all Virtual CPUs, other than Virtual CPU 0, will perform an incrementing address loop.
  • Burnct= - Specifies the number of BrCT instructions (0 through 2147483647) to be executed after each page is read and/or changed to "burn" additional cycles. The number of cycles actually "burned" is hardware dependent.
  • Cpus= - Specifies the total number of virtual CPUs (1 through 64) to be defined and used.
  • Exitcmd= - Specifies CP command(s) to be issued via Diagnose x'08' when the program has ended normally. The default is "MSG * VIRSTOEX Ended, Loading Wait PSW".
  • Fwait= - Specifies a fixed number of milliseconds (0 through 999999) to wait between loops.
  • Go= - Specifies the number of seconds (0 through 43200) after program start at which the thrashing phase is allowed to begin. If a value of 0 is specified, then the thrashing phase is allowed to begin as soon as possible. This parameter allows coordinated starting of the thrashing phase when the measurement involves multiple concurrent instances of the program. The priming phase, if any, always runs to completion, regardless of the value of Go=.
  • Handicap= - Specifies that the CPU utilization (0 through 100) for the specified Virtual CPU (00 through 3F) is to be limited to the specified target utilization.
  • Increment= - Specifies the address increment (1 through 1048576) in KB to be used.
  • Justvtime - Specifies that the target CPU utilization for each Virtual CPU is to be based on the virtual time used and not the total time used.
  • Loops= - Specifies the maximum number of loops (0 through 2147483647) for all Virtual CPUs combined.
  • Msgon - Specifies that all program messages, including interim progress progress messages at the end of each loop, are to be generated.
  • Nwait= - Specifies a fixed number of milliseconds (0 through 999999) to wait when a Stopchk occurs on a Virtual CPU other than Virtual CPU 0.
  • Pprime - Specifies that a priming pass to build Page and Segment Tables, by using an increment of 1MB and changing the data in each page, will be executed before the normal program execution begins. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program and all other program parameters will be ignored during the priming pass.
  • Querymsg= - Specifies the number of seconds (0 through 999) between interim progress messages. The program will write interim progress messages to the console to report the elapsed time, the number of pages referenced, and the rate at which pages were referenced since the last interim progress message. The messages will be written by each Virtual CPU.
  • RDpct= - Specifies the percentage of pages (1 through 100) which should be referenced in each loop. A priming pass to populate storage and build storage management tables, by using the Increment= value and changing the data in each page, will be executed before the normal program execution begins. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program and all other program parameters will be ignored during the priming pass.
  • RWait= - Specifies a maximum number of milliseconds (0 through 999999) to wait between loops. The actual number of milliseconds will be a random number between 0 and nnnnnn, which will be calculated at the end of each loop.
  • Stopchk= - Specifies the number of pages (0 through 268435456) to be referenced before performing an interim time limit check. The time limit will be checked each time the specified number of pages have been referenced. This allows more precise control of the program when a loop takes several minutes (e.g. in a 1 TB user). When the program is stopped in this manner, the loop count will be incorrect but the page count, elapsed time, and page rate will be correct.
  • Time= - Specifies the maximum number of seconds (0 through 43200) to run the program.
  • Uprime - Specifies that a priming pass to build Upper DAT Tables, by using an increment of 2 GB and changing the data in each page, will be executed before the normal program execution begins. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program and all other program parameters will be ignored during the priming pass.
  • Vprime - Specifies that a priming pass to populate storage and build storage management tables, by using the specified increment (1 through 1048576), in KB, and changing the data in each page, will be executed before the normal program execution begins. The time used and the number of pages referenced will not be included in the statistics produced at the end of the program and all other program parameters will be ignored during the priming pass.
  • Wrpct= - Specifies the percentage of pages (0 through 100) which should be changed in each loop.
  • Xwait= - Specifies a multiplier (1 through 999) to be applied to Fwait= or RWait= time for all Virtual CPUs except Virtual CPU 0.
  • Yieldpct= - Specifies the maximum CPU utilization target (1 through 100) for each Virtual CPU. If the calculated utilization is higher than the target, the Virtual CPU will yield control and enter a Wait State for a duration calculated to bring its utilization down to the target. The calculated utilization is based on the total time used unless the Justvtime parameter is specified, in which case it will be based on the virtual time used.
  • Zwait= - Specifies a fixed number of milliseconds (0 through 999999) to wait when a Stopchk occurs on Virtual CPU 0.

The following default values are used if no parameters are specified.

            AE: Off
            AN: Off
            AO: Off
            AZ: Off
        Burnct: 0
          Cpus: 7
       Exitcmd: MSG * VIRSTOEX Ended, Loading Wait PSW
         Fwait: 0
            Go: 0
      Handicap: 100 (if Yieldpct was not specified)
     Increment: 1024 (1024 KB or 1 MB)
     Justvtime: Off
         Loops: 0
         Msgon: Off
         Nwait: 0
        Pprime: Off
      Querymsg: 0
         RDpct: 100
         RWait: 0
       Stopchk: 0
          Time: 0
        Uprime: Off
        Vprime: 0
         Wrpct: 100
         Xwait: 1
      Yieldpct: 100
         Zwait: 0

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