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HP OpenVMS Systemsask the wizard |
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The Question is: How can I determine the CPU-usage of a system by using C-functions. I want the same information as I get with the 'monitor system' command (CPU busy) The Answer is : There is no documented interface to MONITOR, but with access to the OpenVMS source listings CD-ROM set (Order QB-MT1AB-E8 for OpenVMS Alpha, QB-001AB-E8 for OpenVMS VAX) and look at the facility [MONTOR] (yes, "MONTOR", not "MONITOR"), and specifically look at the (undocumented, unsupported, and subject to change without notice) exe$getspi interface used within MONITOR. (You will need to LINK against a MONITOR shareable image to resolve your references to the exe$getspi interface.) Alternatively, you will want to acquire and read through the Internals and Data Structures Manual (editions for OpenVMS VAX and OpenVMS Alpha) from Digital Press (www.bh.com) and create a small kernel-mode routine to acquire the information from the vector that is the source of the information reported by MONITOR and other utilities In the per-CPU database referenced by the SMP$GL_CPU_DATA address, look at the CPU$Q_NULLCPU cell for each CPU. Additionally, the SNMP MIB for OpenVMS containing performance data may be of interest. The OpenVMS Wizard would not be surprised to learn there are various programs available from the Encompass (formerly DECUS) library and from other sources that could be used as examples of the exe$getspi and/or the kernel per-CPU database. One such example of calling the MONITOR interface exe$getspi is included on various of the OpenVMS Freeware: [SRH_EXAMPLES]I_SPI.* and related. Also potentially of interest will be the OpenVMS Galaxy GCU processor load-balancing and SMP process/processor (re)scheduling example, provided on V7.2 and later releases: sys$example:GCU$BALANCER.C. A related class scheduler example is available in sys$examples:class.c With OpenVMS V7.3 and later, the (undocumented and unsupported) exe$getspi interface was replaced with the (documented and supported) sys$getrmi interface. Related topics in Ask The Wizard include (2), (697), (1639), (3398), (3687), (4059), (4626), (5235), (5702), (7054), (7155), and likely others.
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