Code location sensitivity of timings

[RuiLoureiro]

File length = 977412

1484 ms
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Press any key to continue ...

[RuiLoureiro]

1344 ms
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1343 ms
2016 ms...

1343 ms
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1344 ms
2015 ms...

1344 ms
1359 ms
1344 ms
2016 ms
If we remove the worst case ...

[RuiLoureiro]

If i am not wrong, you are using 2 counters:
           First  counter     = 1000
           Second counter = count (=4000,etc.)

You get the result only when
the first counter is 0 (counter_end).
So the result has something to do with the execution
of this:

Code: [Select]

   mov edi,count
   mov ebx,esp
   .while edi
       pushargs
       call esi
       mov esp,ebx
       dec edi
Is there any particular reason for this ?

   counter_begin 1000, HIGH_PRIORITY_CLASS
   mov edi,count
   mov ebx,esp
   .while edi
       pushargs
       call esi
       mov esp,ebx
       dec edi
   .endw
   counter_end

[jj2007]

Check if the align is really needed

I normally tune them from the list file in the end

What I intended is that rep movsX may not need ANY alignment, simply because it isn't a loop at this level (at micro code level, it is of course a loop).

Intel(R) Celeron(R) M CPU        420  @ 1.60GHz (MMX, SSE, SSE2, SSE3)
movsd align 16  10476 µs
movsd align 3   10456 µs
movsd align 13  10347 µs
movsb align 16  10510 µs
movsb align 3   10503 µs
movsb align 13  10407 µs

movsd align 16  10514 µs
movsd align 3   10469 µs
movsd align 13  10516 µs
movsb align 16  10455 µs
movsb align 3   10515 µs
movsb align 13  10502 µs

movsd align 16  10526 µs
movsd align 3   10455 µs
movsd align 13  10469 µs
movsb align 16  10360 µs
movsb align 3   10485 µs
movsb align 13  10456 µs

Sample:
test4a proc uses esi edi ecx
  align 16
  nops 3
  rep movsb
  ret
test4a endp


Interesting, though, that movsb is indeed equally fast on my trusty old Celeron, at least for a 10 MB string.

[nidud]

deleted

[Gunther]

That's the result by memcpy.exe by 1234.zip:

Code: [Select]

Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (SSE4)
----------------------------------------------
-- aligned strings --
498952    cycles -  10 (  0) 0: crt_memcpy
898756    cycles -  10 ( 75) 1: movsd - mov eax,ecx
903577    cycles -  10 ( 75) 2: movsd - push ecx
354813    cycles -  10 ( 59) 3: movsb
487954    cycles -  10 (182) 4: SSE
-- unaligned strings --
494936    cycles -  10 (  0) 0: crt_memcpy
895940    cycles -  10 ( 75) 1: movsd - mov eax,ecx
895968    cycles -  10 ( 75) 2: movsd - push ecx
373553    cycles -  10 ( 59) 3: movsb
491344    cycles -  10 (182) 4: SSE
-- short strings 15 --
175961    cycles - 8000 (  0) 0: crt_memcpy
361324    cycles - 8000 ( 75) 1: movsd - mov eax,ecx
361586    cycles - 8000 ( 75) 2: movsd - push ecx
313550    cycles - 8000 ( 59) 3: movsb
92719     cycles - 8000 (182) 4: SSE
-- short strings 271 --
841879    cycles - 8000 (  0) 0: crt_memcpy
780741    cycles - 8000 ( 75) 1: movsd - mov eax,ecx
806939    cycles - 8000 ( 75) 2: movsd - push ecx
623419    cycles - 8000 ( 59) 3: movsb
275466    cycles - 8000 (182) 4: SSE
-- short strings 2014 --
1002628   cycles - 4000 (  0) 0: crt_memcpy
2239737   cycles - 4000 ( 75) 1: movsd - mov eax,ecx
2226209   cycles - 4000 ( 75) 2: movsd - push ecx
962207    cycles - 4000 ( 59) 3: movsb
972245    cycles - 4000 (182) 4: SSE
--- ok ---

Gunther

[RuiLoureiro]

The macro can only be called by EDI, ESI, or EBX or an immediate value.
I think I just run out of regs once and inserted a loop.
The count for small functions is also rather high so it's
just a way of skipping zeros I guess.

    I think you are talking about this macro:
   
        counter_begin MACRO loopcount:REQ, priority
   or  counter_end

    If it is, we cannot use EBX because cpuid destroys EBX

I modified counter_begin -written by MichaelW- to this:
(COUNTERLOOPS=1000 or 10000 or 100000 or ...)

Code: [Select]

; this macro uses EDI inside = length from kIni to kEnd
; we need to define an array to save the means.
; we need to define _LoopCount,_MaxLength...etc. in .DATA
BEGIN_COUNTER_CYCLE_HIGH_PRIORITY_CLASS MACRO   kIni, kEnd
                                        LOCAL   labelA,labelB

                mov     _LoopCount, COUNTERLOOPS
                mov     _MaxLength, kEnd
                mov     edi, kIni
                ;mov     _MinLength, edi         ;; not used yet
                mov     _MeanValue, 0           ;; mean is 0

                invoke  GetCurrentProcess
                invoke  SetPriorityClass, eax, HIGH_PRIORITY_CLASS

    labelA:                                         ;; Begin test loop
   
                BEGIN_LOOP_TEST equ <labelA>
           
                xor     eax, eax        ;; Use same CPUID input value for each call
                cpuid                   ;; Flush pipe & wait for pending ops to finish
                rdtsc                   ;; Read Time Stamp Counter

                push    edx             ;; Preserve high-order 32 bits of start count
                push    eax             ;; Preserve low-order 32 bits of start count
           
                mov     _LoopCounter, COUNTERLOOPS
                xor     eax, eax
                cpuid                   ;; Make sure loop setup instructions finish
          ALIGN 16                      ;; Optimal loop alignment for P6
          @@:                           ;; Start an empty reference loop
                sub     _LoopCounter, 1
                jnz     short @B

                xor     eax, eax
                cpuid                   ;; Make sure loop instructions finish
                rdtsc                   ;; Read end count
                pop     ecx             ;; Recover low-order 32 bits of start count
                sub     eax, ecx        ;; Low-order 32 bits of overhead count in EAX
                pop     ecx             ;; Recover high-order 32 bits of start count
                sbb     edx, ecx        ;; High-order 32 bits of overhead count in EDX
                push    edx             ;; Preserve high-order 32 bits of overhead count
                push    eax             ;; Preserve low-order 32 bits of overhead count

                xor     eax, eax
                cpuid
                rdtsc
                push    edx             ;; Preserve high-order 32 bits of start count
                push    eax             ;; Preserve low-order 32 bits of start count
                ;;-------------------------------------
                ;;              Start
                ;;-------------------------------------
                mov         _LoopCounter, COUNTERLOOPS
                xor         eax, eax
                cpuid                   ;; Make sure loop setup instructions finish
    ALIGN 16                            ;; Optimal loop alignment for P6
    labelB:                             ;; Start test loop
                START_LOOP_TEST equ <labelB>
ENDM
; ------------------------------------------------------------------------
END_COUNTER_CYCLE       MACRO  arg
                        LOCAL  $tmpstr$

                sub         _LoopCounter, 1
                jnz         START_LOOP_TEST                ;; goto labelB
                ;;---------------------------
                ;;   stop this count
                ;;---------------------------
                xor         eax, eax
                cpuid                       ;; Make sure loop instructions finish
                rdtsc                       ;; Read end count
                pop         ecx             ;; Recover low-order 32 bits of start count
                sub         eax, ecx        ;; Low-order 32 bits of test count in EAX
                pop         ecx             ;; Recover high-order 32 bits of start count
                sbb         edx, ecx        ;; High-order 32 bits of test count in EDX
                pop         ecx             ;; Recover low-order 32 bits of overhead count
                sub         eax, ecx        ;; Low-order 32 bits of adjusted count in EAX
                pop         ecx             ;; Recover high-order 32 bits of overhead count
                sbb         edx, ecx        ;; High-order 32 bits of adjusted count in EDX

                mov         DWORD PTR _CounterQword, eax
                mov         DWORD PTR _CounterQword + 4, edx
                finit
                fild        _CounterQword
                fild        _LoopCount
                fdiv
                fistp       _CounterQword

                mov         ebx, dword ptr _CounterQword
               
                ;---------------------------------------------------
                ;               print cycles
                ;---------------------------------------------------
                add         ebx, _MeanValue
                mov         _MeanValue, ebx

                add         edi, 1
                cmp         edi, _MaxLength
                jbe         BEGIN_LOOP_TEST                      ;; goto labelA

                invoke      GetCurrentProcess
                invoke      SetPriorityClass, eax, NORMAL_PRIORITY_CLASS
               
                ; --------------------------------------------------
                ;          Save mean and print mean               
                ; --------------------------------------------------
                invoke      SaveMeans, ebx          ;; save it in one array
                                                       ;; one after another
               
                ;---------------------------------------------------
                print       str$(ebx)                       
                $tmpstr$    CATSTR <chr$(">, <arg>, <",13,10)>       
                print       $tmpstr$
                ;---------------------------------------------------                 
ENDM


Code: [Select]

.data
ALIGN 8                         ;; Optimal alignment for QWORD
_CounterQword   dq 0
_LoopCount      dd 0
_LoopCounter    dd 0                                   

_MinLength      dd 0
_MaxLength      dd 0
_MeanValue      dd 0
;------------------------------
ALIGN   4
                dd 0                ; <<<--- start with 0   
_TblTiming0     dd 600 dup (?)
.code
SaveMeans       proc        kMean:DWORD                   
                mov         eax, kMean
                mov         edx, offset _TblTiming0                   
                mov         ecx, [edx-4]            ; number of means
                mov         [edx+ecx*4], eax                   
                add         ecx, 1
                mov         [edx-4], ecx
                ret
SaveMeans       endp


[nidud]

deleted

[Gunther]

Hi nidud,

I added some bits to Dave's test:

there's nothing attached.

Gunther

[nidud]

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[nidud]

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[jj2007]

Intel(R) Celeron(R) M CPU        420  @ 1.60GHz (SSE3)
-----------------------------------------------
-- aligned strings --
995933  cycles - 10 (  0) 0: crt_strrchr
995891  cycles - 10 ( 40) 1: strrchr
273823  cycles - 10 (154) 2: x
94668   cycles - 10 (112) 3: SSE
-- unaligned strings --
996477  cycles - 10 (  0) 0: crt_strrchr
997094  cycles - 10 ( 40) 1: strrchr
298219  cycles - 10 (154) 2: x
121529  cycles - 10 (112) 3: SSE
-- small strings 128 --
324263  cycles - 500 (  0) 0: crt_strrchr
323710  cycles - 500 ( 40) 1: strrchr
84786   cycles - 500 (154) 2: x
34915   cycles - 500 (112) 3: SSE
-- small strings 1 --
67914   cycles - 500 (  0) 0: crt_strrchr
67286   cycles - 500 ( 40) 1: strrchr
12595   cycles - 500 (154) 2: x
16622   cycles - 500 (112) 3: SSE

[Gunther]

Hi nidud,

here's the output of auto.zip:

Code: [Select]

Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (AVX)
----------------------------------------------
-- aligned strings --
491469    cycles -  10 (  0) 0: crt_memcpy
889651    cycles -  10 ( 63) 1: movsd - mov eax,ecx
887273    cycles -  10 ( 63) 2: movsd - push ecx
355080    cycles -  10 ( 51) 3: movsb
487046    cycles -  10 (182) 4: SSE
355990    cycles -  10 (  0) 5: auto
-- unaligned strings --
490269    cycles -  10 (  0) 0: crt_memcpy
886259    cycles -  10 ( 63) 1: movsd - mov eax,ecx
886778    cycles -  10 ( 63) 2: movsd - push ecx
372520    cycles -  10 ( 51) 3: movsb
491780    cycles -  10 (182) 4: SSE
378881    cycles -  10 (  0) 5: auto
-- short strings 15 --
174897    cycles - 8000 (  0) 0: crt_memcpy
349626    cycles - 8000 ( 63) 1: movsd - mov eax,ecx
343812    cycles - 8000 ( 63) 2: movsd - push ecx
307384    cycles - 8000 ( 51) 3: movsb
98073     cycles - 8000 (182) 4: SSE
293479    cycles - 8000 (  0) 5: auto
-- short strings 271 --
832627    cycles - 8000 (  0) 0: crt_memcpy
773797    cycles - 8000 ( 63) 1: movsd - mov eax,ecx
764418    cycles - 8000 ( 63) 2: movsd - push ecx
586580    cycles - 8000 ( 51) 3: movsb
279676    cycles - 8000 (182) 4: SSE
557134    cycles - 8000 (  0) 5: auto
-- short strings 2014 --
998188    cycles - 4000 (  0) 0: crt_memcpy
2198740   cycles - 4000 ( 63) 1: movsd - mov eax,ecx
2195833   cycles - 4000 ( 63) 2: movsd - push ecx
935710    cycles - 4000 ( 51) 3: movsb
961563    cycles - 4000 (182) 4: SSE
906474    cycles - 4000 (  0) 5: auto
--- ok ---

Gunther

[nidud]

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[nidud]

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