英特尔“退休"是什么意思? [英] What does Intel mean by "retired"?
问题描述
请注意，我已经阅读了英特尔的性能分析指南，其中指出已退休"具有非常精确的含义(第8页)，请参阅第7页上的图.但是，我认为我缺乏了解Retirement / Writeback的确切含义的背景知识.该过程到底是什么?涉及什么?
Note that I have already looked at Intel's Performance Analysis Guide, which states that "retired" has a very precise meaning (on page 8), referring to the diagram on page 7, but I think I lack the background knowledge to understand exactly what is mean by Retirement / Writeback. What exactly is that process and what does it involve?
推荐答案
在上下文中，已退休"是指:指令( ，μop)离开退休部门".这意味着在乱序 CPU管道中，指令最终得以执行，其结果正确无误，并且在建筑状态中可见，就像它们按顺序执行一样.在性能上下文中，这是您应该检查的数量，以计算实际执行了多少指令(具有有用的输出).如果您的环境是节能的，则可以检查在OOO管道("ISSUED"计数器或"EXECUTED"计数器)中开始执行多少条指令，然后将其与退出操作的计数进行比较；高的差异表明CPU会做很多无用的工作，并且会消耗过多的电量.
In the context "retired" means: the instruction (microoperation, μop) leaves the "Retirement Unit". It means that in Out-of-order CPU pipeline the instruction is finally executed and its results are correct and visible in the architectural state as if they execute in-order. In performance context this is the number you should check to compute how many instructions were really executed (with useful output). If your context is energy saving, you may check how many instructions started their execution in OOO pipeline ("ISSUED" counter or "EXECUTED" counter) and compare the number with count of retired operation; high difference shows that CPU does a lot of useless work and uses excess power.
此处是退休部门的简短说明: http://users.utcluj.ro /~baruch/book_ssce/SSCE-Intel-Pipeline.pdf
Short description of the Retirement unit is here: http://users.utcluj.ro/~baruch/book_ssce/SSCE-Intel-Pipeline.pdf
5.4.7.4.退休单位
5.4.7.4. Retirement Unit
引退单元将推测执行的微操作的结果写入用户可见的寄存器，并从重排序缓冲区中删除微操作.类似于保留站，引退单元不断检查重新排序缓冲区中微操作的状态，以查找已执行且不再与指令池中的其他微操作有任何依赖关系的微操作.然后，它将按其原始程序顺序退出已完成的微操作.
The retirement unit writes the results of speculatively executed microoperations into the user-visible registers and removes the microoperations from the reorder buffer. Like the reservation station, the retirement unit continuously checks the status of microoperations in the reorder buffer, looking for ones that have been executed and no longer have any dependencies with other microoperations in the instruction pool. It then retires completed microoperations in their original program order.
引退单元可以在每个时钟周期引退三个微操作(/<-可能已过时/).退出微操作时，它会将结果写入处理器的寄存器文件和/或内存中.写入结果后，将微操作从重新排序缓冲区中删除.
The retirement unit can retire three microoperations per clock cycle (/<-- this may be outdated/). In retiring a microoperation, it writes the results to the processor’s register file and/or memory. After the results have been written, the microoperation is removed from the re-order buffer.
有关单位的更多详细信息，在这里(由Agner Fog提供) http://www.agner.org/optimize/microarchitecture .pdf 章为您的CPU退休"
More detailed information about unit is here (by Agner Fog) http://www.agner.org/optimize/microarchitecture.pdf chapter Retirement for your CPU
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