kmem_cache_init函数问题

embeddedlwp

这个函数看得我的很晕，说出自己理解，希望不对的地方请高手指正

1. 529static struct arraycache_init initarray_cache __initdata =
   
2. 530        { { 0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
   
3. 531static struct arraycache_init initarray_generic =
   
4. 532        { { 0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
   
5. 
   
6. 
   
7. cache_cache.array[smp_processor_id()] = &initarray_cache.cache;
   

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kmem_cache_init的流程是不是：

先用一个静态定义cache即initarray_cache.cache充当cache_cache的local cache

然后create kmalloc caches使用下边一个循环

1. 797        while (sizes->cs_size) {
   
2. 798                /* For performance, all the general caches are L1 aligned.
   
3. 799                 * This should be particularly beneficial on SMP boxes, as it
   
4. 800                 * eliminates "false sharing".
   
5. 801                 * Note for systems short on memory removing the alignment will
   
6. 802                 * allow tighter packing of the smaller caches. */
   
7. 803                sizes->cs_cachep = kmem_cache_create(names->name,
   
8. 804                        sizes->cs_size, ARCH_KMALLOC_MINALIGN,
   
9. 805                        (ARCH_KMALLOC_FLAGS | SLAB_PANIC), NULL, NULL);
   
10. 806
    
11. 807                /* Inc off-slab bufctl limit until the ceiling is hit. */
    
12. 808                if (!(OFF_SLAB(sizes->cs_cachep))) {
    
13. 809                        offslab_limit = sizes->cs_size-sizeof(struct slab);
    
14. 810                        offslab_limit /= sizeof(kmem_bufctl_t);
    
15. 811                }
    
16. 812
    
17. 813                sizes->cs_dmacachep = kmem_cache_create(names->name_dma,
    
18. 814                        sizes->cs_size, ARCH_KMALLOC_MINALIGN,
    
19. 815                        (ARCH_KMALLOC_FLAGS | SLAB_CACHE_DMA | SLAB_PANIC),
    
20. 816                        NULL, NULL);
    
21. 817
    
22. 818                sizes++;
    
23. 819                names++;
    
24. 820        }

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第一次循环中，第803行，为malloc_sizes创建各个cache，此时使用下边这个设置第一个local cache

1. if (g_cpucache_up == NONE) {
   
2. 1426          /* Note: the first kmem_cache_create must create
   
3. 1427           * the cache that's used by kmalloc(24), otherwise
   
4. 1428           * the creation of further caches will BUG().
   
5. 1429           */
   
6. 1430        cachep->array[smp_processor_id()] = &initarray_generic.cache;
   
7. 1431        g_cpucache_up = PARTIAL;

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而执行到813行的时候，已经使用kmalloc，从刚才的那个initarray_generic.cache分配描述符了：

1. cachep->array[smp_processor_id()] = kmalloc(sizeof(struct arraycache_init),GFP_KERNEL);

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直到while循环结束都是通过kmalloc从initarray_generic.cache分配描述符

这样用于kmalloc的普通高速缓存cache_sizes就建立好了。下一步是将刚才的那两个静态定义的local cache重新用kmalloc分配

然后调用enable_cpucache函数中为每个cache重新建立local cache

wangjianchangdx

1. /*
   
2. * Initialisation.  Called after the page allocator have been initialised and
   
3. * before smp_init().
   
4. */
   
5. void __init kmem_cache_init(void)
   
6. {
   
7.         ***
   
8.         /* Bootstrap is tricky, because several objects are allocated
   
9.          * from caches that do not exist yet:
   
10.          * 1) initialize the cache_cache cache: it contains the struct
    
11.          *    kmem_cache structures of all caches, except cache_cache itself:
    
12.          *    cache_cache is statically allocated.
    
13.          *    Initially an __init data area is used for the head array and the
    
14.          *    kmem_list3 structures, it's replaced with a kmalloc allocated
    
15.          *    array at the end of the bootstrap.
    
16.          * 2) Create the first kmalloc cache.
    
17.          *    The struct kmem_cache for the new cache is allocated normally.
    
18.          *    An __init data area is used for the head array.
    
19.          * 3) Create the remaining kmalloc caches, with minimally sized
    
20.          *    head arrays.
    
21.          * 4) Replace the __init data head arrays for cache_cache and the first
    
22.          *    kmalloc cache with kmalloc allocated arrays.
    
23.          * 5) Replace the __init data for kmem_list3 for cache_cache and
    
24.          *    the other cache's with kmalloc allocated memory.
    
25.          * 6) Resize the head arrays of the kmalloc caches to their final sizes.
    
26.          */

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2.6.35.7代码中的注释，其后还有一个

1. void __init kmem_cache_init_late(void)

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