THPDFRangeCacheStatistics Record

Snapshot of source reads, cache hits, prefetch activity, read-ahead depth, and admission counters for the coalescing range cache

Declaration

THPDFRangeCacheStatistics= record
  SourceReadCount: Int64;
  SourceBytesRead: Int64;
  CacheHitCount: Int64;
  CacheMissCount: Int64;
  PrefetchRequestCount: Int64;
  PrefetchCompletedCount: Int64;
  PrefetchCancelledCount: Int64;
  SequentialReadCount: Int64;
  RandomReadCount: Int64;
  SuppressedPrefetchCount: Int64;
  CurrentReadAheadBlocks: Integer;
  PeakReadAheadBlocks: Integer;
  DirectTransferCount: Int64;
  DirectTransferBytes: Int64;
  CachedRangeCount: Integer;
  CachedBytes: Int64;
  AdmissionCount: Int64;
  RejectionCount: Int64;
  EvictionCount: Int64;
  FrequencyAdmissionCount: Int64;
  FrequencyRejectionCount: Int64;
  FrequencyAgingCount: Int64;
end;

Unit

HPDFDoc

Fields

Field	Purpose
`SourceReadCount`	Number of reads issued to the underlying source
`SourceBytesRead`	Bytes pulled from the underlying source
`CacheHitCount`	Read requests served entirely from cached ranges
`CacheMissCount`	Read requests that required source access
`PrefetchRequestCount`	Background prefetch ranges requested
`PrefetchCompletedCount`	Background prefetch ranges that finished
`PrefetchCancelledCount`	Background prefetch ranges cancelled, typically by foreground demand
`SequentialReadCount`	Reads classified as sequential in the access pattern detector
`RandomReadCount`	Reads classified as random
`SuppressedPrefetchCount`	Prefetch attempts suppressed by the admission heuristics
`CurrentReadAheadBlocks`	Read-ahead depth currently used by the adaptive controller
`PeakReadAheadBlocks`	Highest read-ahead depth reached
`DirectTransferCount`	Transfers that bypassed the cache entirely
`DirectTransferBytes`	Bytes moved by bypass transfers
`CachedRangeCount`	Cache entries currently resident
`CachedBytes`	Bytes currently held by cache entries
`AdmissionCount`	Ranges admitted into the cache
`RejectionCount`	Ranges refused admission by size or policy limits
`EvictionCount`	Cache entries evicted to respect byte and entry budgets
`FrequencyAdmissionCount`	Admissions credited by the frequency sketch as reused blocks
`FrequencyRejectionCount`	Admissions refused because the frequency sketch saw no reuse
`FrequencyAgingCount`	Aging operations performed on the frequency sketch

Usage notes

Read it with the cache source's GetStatistics method; the snapshot is taken under the cache lock so it is internally consistent
A high SuppressedPrefetchCount together with a low hit rate suggests random access where prefetching does not pay off
CachedRangeCount, CachedBytes, and FrequencyAgingCount are sampled live from the cache rather than accumulated

THPDFRangeCacheStatistics Record

Declaration

Unit

Fields

Usage notes

Related APIs