如何计算有效CPI为3级缓存 [英] How to calculate effective CPI for a 3 level cache
问题描述
我绝望地卡在一门功课的问题，我希望一些帮助理解的更好。下面是我得到了什么：
I am hopelessly stuck on a homework problem, and I would love some help understanding it better. Here is what I was given:
- CPU底座CPI = 2，时钟频率2GHz的=
- 主缓存，速率小姐/指令= 7％
- L-2高速缓存访问时间为15ns =
- L-2高速缓存，本地缺失率/指令= 30％
- L-3高速缓存访问时间为30ns =
- L-3高速缓存，环球小姐速率/指令= 3％，主存储器存取时间= 150ns的
什么是有效的 CPI 的？
这是我的理解是，我需要计算每个高速缓存级别的缺失损失。
It is my understanding that I need to calculate the miss penalty for each cache level.
- L2的L1缺失损失=访问时间= 15ns的/（1纳秒/ 2毫升）= 30个时钟周期
- L3的L2缺失损失=访问时间30ns的= /（1纳秒/ 2毫升）= 60个时钟周期
- MM = 150ns的/（1纳秒/ 2毫升）= 300个时钟周期的L3缺失损失=访问时间
现在我需要计算有效的 CPI 的。这是我有点糊涂了。
Now I need to calculate the effective CPI. This is where I am a bit confused.
我相信的公式的应该是：
CPI = BaseCPI +（％L1 MR / INSTR * L1小姐罚款）+（％L1 MR / INSTR *
％L2 MR / INSTR * L2小姐罚款）+（％全球MR / INSTR * L3小姐罚款）
CPI = BaseCPI + (%L1 MR/Instr * L1 Miss Penalty) + (%L1 MR/Instr * %L2 MR/Instr * L2 Miss Penalty) + (%Global MR/Instr * L3 Miss Penalty)
如果我这样做，我得到
CPI = 2.0 +（0.07 * 30）+（0.07 * 0.3 * 60）+（0.03 * 300）= 14.36
CPI = 2.0 + (0.07 * 30) + (0.07 * 0.3 * 60) + (0.03 * 300) = 14.36
电子邮件我的老师，因为没有人在课堂上理解全球和本地的1-2分钟的解释之后，我被告知，我的答案是接近的，但错了。如果任何人都可以提供一些见解，甚至是指向我朝着一个很好的教程，我将不胜感激。我能理解如何找出有效的 CPI 的1和2级高速缓存。使得跳转到3混淆了我。
After emailing my instructor because no one in the class understood the 1-2 minute explanation of global and local, I was told that my answer is close, but wrong. If anyone could provide some insight, or even point me towards a good tutorial, I would be grateful. I can understand how to figure out effective CPI for 1 and 2 level caches. Making the jump to 3 confuses me.
推荐答案
哎，所以我给他发邮件询问该解决方案
Hey so I emailed him asking about this solution
有效CPI = 2.0 + 0.07×30 + 0.30×60 + 0.03×300 = 31.1
Effective CPI = 2.0 + .07 x 30 + .30 x 60 + .03 x 300 = 31.1
和他的回应是，L1和L3是正确的，但我不得不考虑到L2当地的命中率。不知道这是什么意思呢，而是希望这个小信息可以帮助
and his response was that L1 and L3 were correct but that I had to take into account the local miss rate for L2. Not sure what that means yet, but hope this little info helps
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