延长在Linux内核中使用的指令集（SSE，MMX）？ [英] Are extended instruction sets (SSE, MMX) used in Linux kernel?

问题描述

好了，他们带来了（应该至少带来）的性能有很大的提高，是不是？

Well, they bring (should bring at least) great increase in performance, isn’t it?

所以，我还没有看到任何Linux内核源，但倒是爱问：是他们以某种方式使用吗？ （在这种情况下 - ？必须有一些特殊的code股的制度，没有这样的说明）

So, I haven’t seen any Linux kernel sources, but ‘d love to ask: are they used somehow? (In this case – there must be some special "code-cap" for system that has no such instructions?)

推荐答案

上证和MMX指令集有音频/视频和游戏工作之外的价值有限。您可能会发现在内核中的黑暗角落几个明确的用途，但我不会指望它。在一般情况下的答案是不，他们不是拿来主义，也不是在大多数非内核/用户空间的应用程序使用。

The SSE and MMX instruction sets have limited value outside of audio/video and gaming work. You might find a few explicit uses in dark corners of the kernel, but I wouldn't count on it. The answer in the general case is "no, they are not used", nor are they used in most non-kernel/userspace applications.

内核有时确实选择使用特定于某些CPU在某些x86指令（如present一些AMD或英特尔模型，但不是全部，也不反之亦然），如系统调用，但这些都是从SIMD指令集不同你指的，而不是一些更广泛的类似主题的扩展的一部分。

The kernel does sometimes optionally use certain x86 instructions that are specific to certain CPUs (e.g. present on some AMD or Intel models but not all, nor vice-versa), such as syscall, but these are different from the SIMD instruction sets you're referring to, and are not part of some wider set of similarly-themed extensions.

在马克的回答，我去寻找。可以轻松地识别正在使用我他们的唯一地方是在的的RAID 6图书馆（其中也有对AltiVec的支持，这是PowerPC SIMD指令集）。

After Mark's answer, I went looking. The only place I could easily identify them being used is in the RAID 6 library (which also has support for AltiVec, which is the PowerPC SIMD instruction set).

（警惕刚刚grepping树，有很多斑点，内核就知道SSE / MMX支持用户空间应用，但实际上并没有使用它。不幸的变量名的还有一对夫妇的情况下，有绝对无关，与SSE，例如在SCTP执行。）

(Be wary just grepping the tree, there are a lot of spots where the kernel "knows" about SSE/MMX to support user-space applications, but isn't actually using it. Also a couple cases of unfortunate variable names that have absolutely nothing to do with SSE, e.g. in the SCTP implementation.)

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