4 ms·
Can someone explain how to read the readings from Instruction Latency(InstLatX86). For example how to read the following line, 201 X86 :INC r8
by iamcreasy 5y ago
Can someone explain how to read the readings from Instruction Latency(InstLatX86).
For example how to read the following line,
201 X86 :INC r8 L: 13.36ns= 1.0c T: 6.68ns= 0.50c
This instruction is incrementing the value of r8 general purpose register. But I am not sure how to parse L: and T: section.
Also, does this number change proportionally if it is in low power mode or if the CPU is undervolted?
- ytch 5y agoThere are some explanation in Comment page: In this dump latency means the time that it takes for the next dependent same-type instruction to start. Throughput means the time that it takes for the next independent same-type instruction to start:
- mkbosmans 5y agoL is the latency of the instruction, so 1 clock cycle after the INC r8 instruction another instruction can operate on the result in r8. T is the reciprocal throughput, meaning in this case that the CPU can sustain 2 INC instructions per clock cycle, if there are no data dependencies of course. In general these numbers will stay the same when counted in clock cycles, regardless of frequency.
- colejohnson66 5y agoTo add: with pipelined processors, it doesn’t make sense to list “clocks per instruction” as a single number. Since the advent of superscalar processors, it makes even less sense. Hence why there’s “latency” and “throughput”.