PERF_DATA_HEADER structure (perflib.h)

Provides information about the PERF_DATA_HEADER block that contains the structure. A PERF_DATA_HEADER block corresponds to one query specification in a query, and consists of a PERF_DATA_HEADER structure followed by a sequence of PERF_COUNTER_HEADER blocks.

Syntax

typedef struct _PERF_DATA_HEADER {
  ULONG      dwTotalSize;
  ULONG      dwNumCounters;
  LONGLONG   PerfTimeStamp;
  LONGLONG   PerfTime100NSec;
  LONGLONG   PerfFreq;
  SYSTEMTIME SystemTime;
} PERF_DATA_HEADER, *PPERF_DATA_HEADER;

Members

dwTotalSize

The sum of the size of the PERF_DATA_HEADER structure and the sizes of all of the PERF_COUNTER_HEADER blocks in the PERF_DATA_HEADER block.

dwNumCounters

The number of PERF_COUNTER_HEADER blocks that the PERF_DATA_HEADER block contains.

PerfTimeStamp

The timestamp from a high-resolution clock.

PerfTime100NSec

The number of 100 nanosecond intervals since January 1, 1601, in Coordinated Universal Time (UTC).

PerfFreq

The frequency of a high-resolution clock.

SystemTime

The time at which data is collected by the provider.

Remarks

The ordering of the PERF_COUNTER_HEADER blocks is based on the Index member of the PERF_COUNTER_IDENTIFIER blocks that the PerfQueryCounterInfo function gets. Each PERF_COUNTER_HEADER block is 8-byte aligned, so the value of the dwTotalSize is a multiple of 8 bytes.

The timestamp information in the PERF_DATA_HEADER structure is required when you compute the display values of certain performance counters.

Requirements

See also

PERF_COUNTER_HEADER

PerfQueryCounterInfo