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KiLog2MaximumIncrement的由来和KiMaximumIncrementReciprocal的由来

article 2025/3/26 2:59:19

第一部分：KiLog2MaximumIncrement的由来

       i = 1;
        j = KeMaximumIncrement;
        while ((1UI64<<i) <= KeMaximumIncrement) {
            i++;
        }
        KiLog2MaximumIncrement = i;

2^17=131072
2^18=262144
i=18=KiLog2MaximumIncrement
中断多久触发一次？使用windbg进入内核态，使用nt!KeMaximumIncrement命令查看看它的值 nt!KeMaximumIncrement=2625a=156250
注意，单位为100ns,因此156250*100/1000/1000=15.625ms

第二部分：KiMaximumIncrementReciprocal的由来

        Temp1 = 1UI64 << (KiLog2MaximumIncrement + 32);
        Temp1 /= KeMaximumIncrement;
        Temp1 -= 1UI64<<32;
        Temp1 += 1;
        KiMaximumIncrementReciprocal = (ULONG) Temp1;
        KeTimerReductionModulus = KeMaximumIncrement * TIMER_TABLE_SIZE;
        ASSERT ((KeTimerReductionModulus / TIMER_TABLE_SIZE) == KeMaximumIncrement);
        Temp1 = 1UI64<<32;
        Temp1 %= KeTimerReductionModulus;
        KiUpperModMul = (ULONG) Temp1;

4000000000000(十六进制) = 1125899906842624(十进制)
1125899906842624/156250=7205759403
100000000(十六进制) = 4294967296(十进制)
7205759403-4294967296=2910792107
2910792107+1=2910792108

2910792108(十进制) = AD7F29AC(十六进制)

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