From reactos@einsurance.de Thu Mar 24 03:35:47 2005
From: Ash <reactos@einsurance.de>
To: ros-dev@reactos.org
Subject: [ros-dev] Speed Tests (was: ping Alex regarding log2() for	scheduler)
Date: Thu, 24 Mar 2005 03:35:41 +0100
Message-ID: <002501c5301a$2c282ac0$3814a8c0@PR0N>
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Hello,

I'd like to provide a small VS.NET project file with 5 different tests.

- 46ffffe9 tells everything is alright with the function calculation
- times are measured with QueryPerformanceCounter
- loop run cnt: 0x2ffffff

result orig function            46ffffe9
it took         1491052
result orig function inlined    46ffffe9
it took         1035547
result second proposal inlined  46ffffe9
it took         1244434
result optimized asm            46ffffe9
it took         1338367
result debug asm                46ffffe9
it took         8774815

The second proposal is the original proposal but more shifts - still slower=20
tho.

Interesting is the inlined version generated by MSVC, shaving off almost 1/3 =

of the overall time.
Also stared as "optimized asm" - no gurantee on register safety tho ;)

For portability and performance sake it should be considered to create a=20
compiler macro.
This function is terribly small, any optimisations inside are outweighted by =

the calling overhead in this case.
The most impressive one is the original function inlined, althought the ASM=20
would only work on x86.

Please do not think about using 64k tables, thats what, 1/2 of a Sempron L2=20
cache?
It would really really trash performance.

Available at: <a href=3D"http://hackersquest.org/kerneltest.html"=20
title=3D"Kernel Test Emulator">Kernel Test</a>

<a=20
href=3D"http://wohngebaeudeversicherung.einsurance.de/">http://wohngebaeudeve=
rsicherung.einsurance.de</a>=20


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