Understanding LinuxNetwork Internals Section 1.2.1

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1.2.1. Memory Caches
The kernel uses the kmalloc and kfree functions to allocate and free a memory block, respectively. The syntax of those two functions is similar to that of the two sister calls, malloc and free, from the libc user-space library. For more details on kmalloc and kfree, please refer to Linux Device Drivers (O'Reilly).
1.2.1.高速缓存
内核分别使用 kmalloc 和 kfree 两个函数分配而且释放一个存储区段。那二个函数的语法与他们两个词的意义类似,malloc 和free, (译注：malloc与free是C++/C语言的标准库函数)  从用户-空间的libc库。关于 kmalloc和 kfree的更多细节, 请查阅 《Linux设备驱动》一书 (O'Reilly).
It is common for a kernel component to allocate several instances of the same data structure type. When allocation and deallocation are expected to happen often, the associated kernel component initialization routine (for example, fib_hash_init for the routing table) usually allocates a special memory cache that will be used for the allocations. When a memory block is freed, it is actually returned to the same cache from which it was allocated.
一个内核结构通常分配一些相同的数据结构类型实例。 当allocation（存储单元配置）和 deallocation（存储单元分配）被期望时常发生，关联的内核成份例行初始化(举例来说, fib_hash_init 对于路由表) 通常会分配一个特别的高速缓存用于分配存储单元。 当一个存储区段被释放的时候, 它实际上被回收到了最初分配它的相同的地方。
Some examples of network data structures for which the kernel maintains dedicated memory caches include:
一些网络数据结构的例子关于一个内核维持高速缓存的 包括:
Socket buffer descriptors
This cache, allocated by skb_init in net/core/sk_buff.c, is used for the allocation of sk_buff buffer descriptors. The sk_buff structure is probably the one that registers the highest number of allocations and deallocations in the networking subsystem.
套接字缓冲描述
一个缓存被 net/core/sk_buff.c 的 skb_init 分配,作为 sk_buff 缓冲描述的分配。 sk_buff 结构或许是一个可注册的最高的数字关于存储单元配置和分配的在网络子系统中。
Neighboring protocol mappings
Each neighboring protocol uses a memory cache to allocate the data structures that store L3-to-L2 address mappings. See Chapter 27.
邻近的协议映射
每个邻近的协议使用一个高速缓存去分配数据结构 存储 L3层-到-L2层 地址映射。 请见第 27 章。
Routing tables
The routing code uses two memory caches for two of the data structures that define routes. See Chapter 32.
Here are the key kernel functions used to deal with memory caches:
路由表
路由代码使用二个高速缓存作为的二个数据结构定义路由。 请见第 32 章。
这里有一些常用来处理高速缓存的关键内核函数:
kmem_cache_create

kmem_cache_destroy
Create and destroy a cache.

kmem_cache_alloc

kmem_cache_free
Allocate and return a buffer to the cache. They are usually called via wrappers, which manage the requests for allocation and deallocation at a higher level. For example, the request to free an instance of an sk_buff buffer with kfree_skb ends up calling kmem_cache_free only when all the references to the buffer have been released and all the necessary cleanup has been done by the interested subsystems (for instance, the firewall).
分配或者回收一个缓冲给缓存。 他们通常被叫做在经由包裹器(wrappers), 在一个较高的级别处理存储单元配置和分配的请求。 举例来说, 一个请求关于释放一个 sk_buff 缓冲经由kfree_skb 的例子 用 kmem_cache_free 只有当所有的涉及的缓冲已经被释放，而且所有必需清除的已经被相关的子系统清除的时候.(举例来说, 防火墙)
The limit on the number of instances that can be allocated from a given cache (when present) is usually enforced by the wrappers around kmem_cache_alloc, and are sometimes configurable with a parameter in /proc.
For more details on how memory caches are implemented and how they interface to the slab allocator, please refer to Understanding the Linux Kernel (O'Reilly).
一个极限情况被分配在能一个给定的缓存 通常在 kmem_cache_alloc 的周围被包裹器运行, 而且有时配置时加一个叁数在 /proc。
对于关于的更多细节，高速缓存如何实现面贮藏和分配成片的分配算法（译注：how they interface to the slab allocator）, 请参阅 《Understanding the Linux Kernel》 (O'Reilly)。


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