访问各种缓存和主内存的大概成本? [英] Approximate cost to access various caches and main memory?

问题描述

谁能告诉我访问 L1、L2 和 L3 缓存以及 Intel i7 处理器上的主内存的大概时间(以纳秒为单位)?

Can anyone give me the approximate time (in nanoseconds) to access L1, L2 and L3 caches, as well as main memory on Intel i7 processors?

虽然这不是一个专门的编程问题，但了解这些速度细节对于一些低延迟编程挑战是必要的.

While this isn't specifically a programming question, knowing these kinds of speed details is neccessary for some low-latency programming challenges.

推荐答案

这是 i7 和 Xeon 系列处理器的性能分析指南.我应该强调，这有你需要的东西，还有更多(例如，查看第 22 页的某些时间和周期).

Here is a Performance Analysis Guide for the i7 and Xeon range of processors. I should stress, this has what you need and more (for example, check page 22 for some timings & cycles for example).

此外，此页面有一些详细信息关于时钟周期等.第二个链接提供以下数字:

Additionally, this page has some details on clock cycles etc. The second link served the following numbers:

Core i7 Xeon 5500 Series Data Source Latency (approximate)               [Pg. 22]

local  L1 CACHE hit,                              ~4 cycles (   2.1 -  1.2 ns )
local  L2 CACHE hit,                             ~10 cycles (   5.3 -  3.0 ns )
local  L3 CACHE hit, line unshared               ~40 cycles (  21.4 - 12.0 ns )
local  L3 CACHE hit, shared line in another core ~65 cycles (  34.8 - 19.5 ns )
local  L3 CACHE hit, modified in another core    ~75 cycles (  40.2 - 22.5 ns )

remote L3 CACHE (Ref: Fig.1 [Pg. 5])        ~100-300 cycles ( 160.7 - 30.0 ns )

local  DRAM                                                   ~60 ns
remote DRAM                                                  ~100 ns

EDIT2:
最重要的是引表下的通知，说:

EDIT2:
The most important is the notice under the cited table, saying:

_{"注意:这些值是粗略的近似值.他们依赖核心和非核心频率、内存速度、BIOS 设置、DIMM 的数量、ETC 等..您的里程可能会有所不同."}

_{"NOTE: THESE VALUES ARE ROUGH APPROXIMATIONS. THEY DEPEND ON CORE AND UNCORE FREQUENCIES, MEMORY SPEEDS, BIOS SETTINGS, NUMBERS OF DIMMS, ETC,ETC..YOUR MILEAGE MAY VARY."}

我应该强调的是，除了时序/周期信息之外，上述英特尔文档还解决了 i7 和至强系列处理器的更多(非常)有用的细节(从性能的角度来看).

I should highlight that, as well as timing/cycle information, the above intel document addresses much more (extremely) useful details of the i7 and Xeon range of processors (from a performance point of view).

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