1// Licensed to the .NET Foundation under one or more agreements.
2// The .NET Foundation licenses this file to you under the MIT license.
3// See the LICENSE file in the project root for more information.
4
5//
6// CycleTimer has methods related to getting cycle timer values.
7// It uses an all-statics class as a namespace mechanism.
8//
9
10#ifndef _CYCLETIMER_H_
11#define _CYCLETIMER_H_
12
13#include "windef.h"
14
15class CycleTimer
16{
17 // This returns the value of the *non-thread-virtualized* cycle counter.
18 static unsigned __int64 GetCycleCount64();
19
20
21 // This wraps GetCycleCount64 in the signature of QueryThreadCycleTime -- but note
22 // that it ignores the "thrd" argument.
23 static BOOL WINAPI DefaultQueryThreadCycleTime(__in HANDLE thrd, __out PULONG64 cyclesPtr);
24
25 // The function pointer type for QueryThreadCycleTime.
26 typedef BOOL (WINAPI *QueryThreadCycleTimeSig)(__in HANDLE, __out PULONG64);
27
28 // Returns a function pointer for QueryThreadCycleTime, or else BadFPtr.
29 static QueryThreadCycleTimeSig GetQueryThreadCycleTime();
30
31 // Initialized once from NULL to either BadFPtr or QueryThreadCycleTime.
32 static QueryThreadCycleTimeSig s_QueryThreadCycleTimeFPtr;
33
34 public:
35
36 // This method computes the number of cycles/sec for the current machine. The cycles are those counted
37 // by GetThreadCycleTime; we assume that these are of equal duration, though that is not necessarily true.
38 // If any OS interaction fails, returns 0.0.
39 static double CyclesPerSecond();
40
41 // Does a large number of queries, and returns the average of their overhead, so other measurements
42 // can adjust for this.
43 static unsigned __int64 QueryOverhead();
44
45 // There's no "native" atomic add for 64 bit, so we have this convenience function.
46 static void InterlockedAddU64(unsigned __int64* loc, unsigned __int64 amount);
47
48 // Attempts to query the cycle counter of the current thread. If successful, returns "true" and sets
49 // *cycles to the cycle counter value. Otherwise, returns false. Note that the value returned is (currently)
50 // virtualized to the current thread only on Windows; on non-windows x86/x64 platforms, directly reads
51 // the cycle counter and returns that value.
52 static bool GetThreadCyclesS(unsigned __int64* cycles);
53};
54
55#endif // _CYCLETIMER_H_
56
57