1. VSD 5.1.1 Release Notes

Changes in statistic types, affecting graphs for combined processes

A number of statistics have changed type and are now of type counter. This impacts the way VSD generates graphs when multiple values are combined, e.g. when looking at such statistics for all Gems in the repository.

The following statistics are affected:

CacheScanCount CleanSlotsRecoveredCount CodeGenFullCount CommitRecordReleases ContinueTransactionCount CrashedSlotsRecoveredCount DataIoOps DiskXfers ExtentGrowTotal ForcedDisconnects InterruptDev InterruptSoft LocalCachePceReclaimCount LoginLogFlushes LoginLogThreadOperations MlClearAllCount MlFullLookupCount MlLuCacheGrowCount MlLuCacheLargeCount MlLuCacheResetCount MlPolyCacheCreateCount MlPolyCacheFullCount MlPolyCacheGrowCount

NewOopRequests NewPagesRequests NumberOfMarkSweeps NumberOfScavenges ObjectsReadInBytes OldGenFullCount OtherIoOps PageCycles PageManagerStarvedCount PageScans PageSteals PermGenFullCount ReadIoOps RejectedProcsCount ReturnOopRequests ReturnPagesRequests SamplesSkipped ScavsPromToMkSwCount StnAioCompleted1Suspend StnAioCompletedNoSleep StnAioCompletedNoSuspend StnAioFsyncCount StnAioLastSuspendCount

StnAioSuspendTimeoutCount StnAioTotalSleepCount StnAioWriteFailures StnLoopCount StnLoopNetPollBeforeSleepCount SystemClockStuckCount SystemFsReads SystemFsWrites SystemNfsBytesRead SystemNfsBytesWritten SystemNfsReads SystemNfsWrites SystemSelects TotalNewObjectsCommitted TotalNewSymbolsCommitted TotalObjectsCommitted TotalSigLostOtRootsSent TotalSigStopSessionsSent TotalSigTermsSentToGems TotalSigTermsSentToPageServers VoteOnDeadCount WriteIoOps

Note that there is no change in how VSD handles counter types in this release. The following discussion describes the way that statistic type affects combining values, to clarify the impact of the change in statistic type.

The type of a statistic is an internal variable in VSD, and may be, for example, counter, counter64, uvalue, or svalue64. The type of a statistic has several affects, including the default filter, which is per-second for counter types and none for uvalue.

The statistic type "counter" is designed for statistics that are written based on the current value of an server variable which is continuously incremented during GemStone operation. The raw data for these values generally start from 0 at the beginning of the process’s lifetime, monotonically increase, and never decrease. For this type of statistic, the value itself is not interesting, it is the changes in value between records that is used for analysis.

Since the changes in value rather than the value itself are of interest, the way these numbers are combined is different between counters and non-counter statistic types, for the case in which there are multiple processes that do not have exactly the same lifetime.

For non-counter types, adding or combining is a simple sum, in which the values for each process that includes a sample value at the given time are added together. If this method was used for counters, it would produce invalid decreases for the total after a process ended; since, for example, the per-second time spent waiting for IO is not actually decreased when a process ends. To avoid this, the algorithm VSD uses to combine values is different for counter type statistics and non-counter types. For counter types, on a chart that shows combined values, for processes that ended before the end of the chart display, the lines continue to include the value of the final sample for process/es that ended. This keeps the per-second graphs correct, but makes the unfiltered combined data higher than would be intuitive.