访问各种缓存和主存储器的大概费用? [英] Approximate cost to access various caches and main memory?

问题描述

有人能给我大概的时间(以纳秒为单位)访问L1，L2和L3缓存以及Intel i7处理器上的主内存吗?

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?

虽然这不是专门针对编程的问题，但了解某些速度细节对于某些低延迟编程挑战是必需的.

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

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，此页面上有一些详细信息时钟周期等.第二个链接提供了以下数字:

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 :
最重要的是被引用的表格下的通知，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.它们取决于 核心和非核心频率，内存速度，BIOS设置， DIMM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."}

我要强调的是，除了时间/周期信息外，上述intel文档还(从性能的角度)介绍了i7和Xeon系列处理器的更多(极其)有用的细节.

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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