Second-level cache pseudo-optimization secrets)

For the role of the processor (CPU) second-level Cache (L2 Cache), we must be more or less familiar with it, even if we do not fully understand the truth, at least the importance can be determined from the price difference between Pentium 4 and celon. The kb level-2 Cache's celon D 2.4GHz is nearly half cheaper than the KB level-2 Cache's Pentium 4 2.4C. What do you think if the Windows XP operating system does not make full use of the CPU's second-level cache? This is a waste of user investment!

In fact, there is a widely spread saying that Windows XP does not optimize the CPU, because it does not enable the second-level cache of the CPU by default. If you open the Registry Editor and find "HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Session Manager \ Memory Management", you can see an item named "SecondLevelDataCache, the default value is "0 ". Obviously, "SecondLevelDataCache" means the second-level data cache. Since it is set to "0", the second-level cache is disabled.

Based on the above arguments, the second-level Cache Optimization Technique emerged, that is, the "SecondLevelDataCache" value is set to the second-level slow storage capacity (unit: KB) of the CPU ). Many optimization software also includes settings for optimizing the CPU second-level cache.

In fact, modifying the value of "SecondLevel DataCache" does not have any optimization effect. Why?
We found the following content in Microsoft's knowledge base: the value of the SecondLevelDataCache key in "HKLM \ SYSTEM \ CurrentControlSet \ Control \ Session Manager \ Memory Management" is read from the Hardware Abstraction Layer (Hardware Abstraction action Layer) of Windows XP) the data of the SecondLevelDataCache key is read only when a failure occurs. In addition, the value of SecondLevelDataCache is 0, indicating that the second-level cache is 256KB.

In a Knowledge Base Article, we also found the words "Do not change the SecondLevelDataCache entry, in this article, it is pointed out that some third-party documents claim that modifying the SecondLevelDataCache key value can improve system performance. The value of the second-level cache is detected by the operating system and is not affected by the SecondLevelDataCache value.

From the Microsoft Knowledge Base Article, we can see that the so-called Windows users need to manually open the second-level cache is wrong. In Windows, the second-level cache value of the CPU is read Based on the hardware abstraction layer. The value of SecondLevelDataCache is read only when reading fails. The default value 0 of SecondLevelDataCache indicates that the second-level cache is 256KB, rather than being disabled. Therefore, the second-level cache of the CPU is enabled at any time, and you do not need to modify it on your own.

Therefore, neither Windows XP nor Vista needs to be optimized, which is purely self-deception.