Alternate timing method for Win 10

[hutch--]

This is a test piece for a late Win 10 API function, QueryUnbiasedInterruptTime. It is supposed to have slightly better precision due to not counting system delays.


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    include \masm32\include64\masm64rt.inc

    .data?
      QueryUnbiasedInterruptTime dq ?

    .code

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 entry_point proc

    USING r12,r13
    LOCAL krnl  :QWORD
    LOCAL rslt1 :REAL8
    LOCAL rslt2 :REAL8
    LOCAL var   :REAL8
    LOCAL text  :QWORD

    LOCAL buff[64]:BYTE
    LOCAL pbuf  :QWORD

    SaveRegs

    HighPriority

    sas text,"1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"

    mov krnl, rvcall(GetModuleHandle,"kernel32.dll")
    mov QueryUnbiasedInterruptTime, rvcall(GetProcAddress,krnl,"QueryUnbiasedInterruptTime")

    conout "Output is in seconds",lf,lf

    mov pbuf, ptr$(buff)                                ; get pointer to buffer

    mov r12, 10                                         ; the iteration counter

  ; *********************************

  lbl:
    rcall QueryUnbiasedInterruptTime,ptr$(rslt1)

    cpuid

  ; =================================

    mov r13, 80000000                                   ; inner loop counter
  cnlp:

  ; ---------------------------------
    rcall StrLen,text                                   ; time StrLen algorithm
  ; ---------------------------------

    sub r13, 1
    jnz cnlp

  ; =================================

    rcall QueryUnbiasedInterruptTime,ptr$(rslt2)

    mov rax, rslt1                                      ; sub result 1 from result 2
    sub rslt2, rax

    cvtsi2sd xmm0, rslt2                                ; convert into to scalar double
    divsd xmm0, AFL8(10000000.0)                        ; divide result by 10 million to get seconds
    movsd var, xmm0                                     ; store the result in the REAL8 variable
    rcall fptoa,var,pbuf                                ; convert result to string
    rcall truncate,pbuf,6                               ; truncate decinal places
    conout "  ",pbuf,lf                                 ; display result

    sub r12, 1
    jnz lbl

  ; *********************************

    conout lf,"Thats all folks ....",lf,lf

    NormalPriority

    waitkey
    RestoreRegs
    .exit

 entry_point endp

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    end

[Siekmanski]

It also runs onder Windows 8.1, don't know if the timings are correct?

Code: [Select]

Output is in seconds

  1.524531
  1.519529
  1.520529
  1.519530
  1.520529
  1.520530
  1.519529
  1.519529
  1.520530
  1.519529

Thats all folks ....

Press any key to continue...


[TimoVJL]

QueryUnbiasedInterruptTime function

Minimum supported client   Windows 7, Windows 8 [desktop apps | UWP apps]


BTW: msvcrt.dll have a _gcvt() function.

Code: [Select]

#pragma comment(lib, "msvcrt.lib")
char *_gcvt(double value, int digits, char *buffer);

int __cdecl main(void)
{
double d = 1.23456;
char buf[100];
puts(_gcvt(d, 16, buf));
return 0;
}


[hutch--]

Yes, that makes sense, its a lot more useful if it runs on Win7 upwards.

[jj2007]

Granularity problem?

Code: [Select]

  1.749100
  1.737099
  1.785102
  1.729098  <-------
  1.729098  <-------
  1.735099
  1.727098  <-------
  1.779101
  1.752100
  1.734099
Second run:

Code: [Select]

  2.107120
  2.106120
  2.106120
  2.105120
  2.105120
  2.105120
  2.105120
  2.105120
  2.105120
  2.105120
Third run:

Code: [Select]

  2.116121
  2.106120
  2.106120
  2.106120
  2.106120
  2.105120
  2.105120
  2.106120
  2.106120
  2.105120

https://docs.microsoft.com/en-us/windows/win32/api/realtimeapiset/nf-realtimeapiset-queryunbiasedinterrupttime

Applications can use the interrupt-time count to measure finer durations than are possible with system time. Applications that require greater precision than the interrupt-time count should use a high-resolution timer. Use the QueryPerformanceFrequency function to retrieve the frequency of the high-resolution timer and the QueryPerformanceCounter function to retrieve the counter's value.

[hutch--]

> Granularity problem?

  1.785102
  1.729098  <-------
  1.729098  <-------
  1.735099
  1.727098  <-------
  1.779101

Probably not, it is fluctuation at a depth of 4 decimal places. The API is still subject to ring0 interference and with much shorter durations it becomes very obvious. The advantage the API is supposed to have is a gain in accuracy by not counting system based pauses and other similar OS based overhead.

[aw27]

May you need QueryUnbiasedInterruptTimePrecise instead   

[aw27]

Actually this QueryUnbiasedInterruptTime, and its cousin QueryUnbiasedInterruptTimePrecise, are not for measuring the time taken by an activity(*) but for measuring the time the system is up discounting Hibernation/Sleep periods.

This can be seen from this code, where the programs sleeps for 1 second with the Sleep function API before calling again QueryUnbiasedInterruptTime:

Code: [Select]

OPTION WIN64:11
OPTION LITERALS:ON
option casemap:none

LPVOID typedef ptr void
TQueryUnbiasedInterruptTime typedef proto :ptr
includelib \masm32\lib64\kernel32.lib
Sleep proto :dword
GetModuleHandleA proto :ptr
GetProcAddress proto :ptr, :ptr
ExitProcess proto :dword
includelib \masm32\lib64\msvcrt.lib
printf proto :ptr, :vararg

.data
KernMod  qword 0
UnbiasedTime qword 0
QueryUnbiasedInterruptTime LPVOID 0
TheTime db "%lld\n",0

.code

main proc
invoke GetModuleHandleA, CSTR("kernel32.dll")
mov KernMod, rax
invoke GetProcAddress, KernMod, CSTR("QueryUnbiasedInterruptTime")
mov r13, rax
mov r12d,0
.while r12d<20
assume r13 : ptr TQueryUnbiasedInterruptTime
invoke r13, addr UnbiasedTime
mov rax, UnbiasedTime
mov rcx, 10000000
mov rdx,0
div rcx
printf("%lld\n", rax)
Sleep(1000)
inc r12d
.endw
invoke ExitProcess,0
main endp

end

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(*) Of course, it can be used to measure the time taken by an activity by subtracting the counter before from the counter after but I don't think is the best function for that. Anyway, it can be tested further and may be there are hidden treasures inside it.