Linux Kernel Memory Management (2)

最新推荐文章于 2025-04-13 13:50:53 发布

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#linux #struct #cache #list #descriptor #object

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本文深入探讨Linux内核的Slab分配器，包括三层架构：Cache、Slab和Object。作者详细介绍了通用缓存和特定缓存的创建与使用，以及Slab和对象的管理。此外，还提到了per-CPU数据结构struct array_cache如何减少锁竞争，并利用硬件缓存。文章还解析了Cache Descriptor的结构，并展示了slabinfo文件如何展示系统中的通用和特定缓存。

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Author: Harold Wang

http://blog.youkuaiyun.com/hero7935

1.Slab Allocator

Three Layer architecture:
--Cache
--Slab
--Object

1.1 Caches
General cache
--kmem_cache_init() and kmem_cache_sizes_init() to establish general cache when system initializing.
--kmalloc() function to allocate object

Specific cache
--caches that are frequently used.
--kmem_cache_create() function to create specific cache

Author: Harold Wang

http://blog.youkuaiyun.com/hero7935

/proc/slabinfo to illustrate the general cache and specific cache in the system.

Linux 2.6 involves per-CPU data structure(struct array_cache which is slab local cache) to reduce spin lock contention among processors and to make better use of the hardware caches, Most allocations and releases of slab objects affects the local cache only!

Cache Descriptor
struct kmem_cache
{
struct kmem_list3* nodelists[MAX_NUMNODES];
/*constructor func*/
/*de-constructor func*/
struct list_head next;
}

struct kmem_list3
{
struct list_head slabs_partial; /* list of slab descriptors with both free and non-free objects */
struct list_head slabs_full; /* list of slab descriptors with non-free objects */
struct list_head slabs_free; /* list of slab descriptors with free objects only */
unsigned long free_objects;/*number of objects available in kmem_list3*/
unsigned int free_limit;/*maxmimum of objects in kmem_list3*/
/*other functions*/
}

struct slab
{
struct list_head list;
unsigned long colouroff;/*offset(in bytes) of the first object in a Slab*/
void* s_mem;/*Address of first object in the slab*/
unsigned int inuse;
kmem_bufctl_t free;/*Index of next free object in the slab, or BUFCTL_END if there are no free objects left*/
}