第一章介紹:ION的框架和buffer的分配;
第二章介紹:如何使用ION buffer;
ION是google在Android4.0 爲了解決內存碎片管理而引入的通用內存管理器,用來支持不同的內存分配機制,如CARVOUT(PMEM),物理連續內存(kmalloc), 虛擬地址連續但物理不連續內存(vmalloc), IOMMU等
(一)ION 概括
Heap: 用來表示內存分配的相關信息,包括id, type, name等。用struct ion_heap表示。
Client: Ion的使用者,用戶空間和內核控件要使用ION的buffer,必須先創建一個client,一個client可以有多個buffer,用struct ion_buffer表示。
Handle: 將buffer該抽象出來,可以認爲ION用handle來管理buffer,一般用戶直接拿到的是handle,而不是buffer。 用struct ion_handle表示。
下面是整個框架的類圖:
說明如下:
在driver初始化過程中會創建ion_device,並提供給用戶層ioctrl接口;不同平臺根據定義好的platform data heap類型創建heap,同時指定這寫heap操作使用的方法接口;不同類型的heap連接成鏈表,保存在通過plist_head heap;
需要使用heap,先註冊client,不同的heap有多個client來使用,連接成鏈表保存在rb_root client;不同的client跟不同的進程pid綁定;
ion_handle管理實際ion_buffer, 成員id:唯一表示ion_buffer的整型變量,通過內核的idr機制加上這個id就可以在其它進程中訪問到這塊buffer。而且上層在傳下來的struct ion_allocation_data結構體中也只是保存了這個id。
用戶空間和內核空間都可以成爲client,不過創建的方法稍稍有點區別;
內核空間:先創建client,有了client之後就可以分配內存,有了handle也就是buffer之後就準備使用了,不過還是物理地址,需要map:
用戶空間:用戶空間如果想使用ION,也必須先要創建client,不過它是打開/dev/ion,實際上它最終也會調用ion_client_create。不過和內核空間創建client的一點區別是,用戶空間不能選擇heap type(使用預訂的heap id隱含heap type),但是內核空間卻可以。另外,用戶空間是通過IOCTL來分配內存的,cmd爲ION_IOC_ALLOC.
ion_fd = open("/dev/ion", O_ RDONLY | O_SYNC);
ioctl(ion_fd, ION_IOC_ALLOC, alloc);
分配好了buffer之後,如果用戶空間想使用buffer,先需要mmap. ION是通過先調用IOCTL中的ION_IOC_SHARE/ION_IOC_MAP來得到可以mmap的fd,然後再執行mmap得到buffer address.然後你也可以將此fd傳給另一個進程,如通過binder傳遞。在另一個進程中通過ION_IOC_IMPORT這個IOCTL來得到這塊共享buffer了。
(二)ION Device和Heap創建
通過ION device和driver匹配之後走入ion_drv_probe()函數:
kernel-4.4/drivers/staging/android/ion/mtk/ion_drv.c
686 static int ion_drv_probe(struct platform_device *pdev)
//創建ion device,name爲ion,並提供應用層操作接口ion_fops;創建調試節點:/sys/kernel/debug/ion
693 g_ion_device = ion_device_create(ion_custom_ioctl);
//ion_custom_ioctl soc自定義的ioctl操作;
698
699 /* create the heaps as specified in the board file */
700 for (i = 0; i < num_heaps; i++) {
701 struct ion_platform_heap *heap_data = &pdata->heaps[i];
702 struct ion_heap *heap;
703
704 if (heap_data->type == ION_HEAP_TYPE_CARVEOUT && heap_data->base == 0) {
705 /* reserve for carveout heap failed */
706 heap_data->size = 0;
707 continue;
708 }
709
710 heap = ion_mtk_heap_create(heap_data);
714
715 ion_device_add_heap(g_ion_device, heap);
716 }
這個函數首先創建一個設備ion_device,通過ion_device_create()來創建,傳入一個給到用戶層面用的ioctl函數:
539 static long _ion_ioctl(struct ion_client *client, unsigned int cmd,
540 unsigned long arg, int from_kernel) {
541 long ret = 0;
542
543 ION_FUNC_ENTER;
544 switch (cmd) {
545 case ION_CMD_SYSTEM:
546 ret = ion_sys_ioctl(client, cmd, arg, from_kernel);
547 break;
548 case ION_CMD_MULTIMEDIA:
549 ret = ion_mm_ioctl(client, cmd, arg, from_kernel);
550 break;
551 }
552 ION_FUNC_LEAVE;
553 return ret;
554 }
處理的ioctrl命令有:
30 enum ION_MM_CMDS {
31 ION_MM_CONFIG_BUFFER,
32 ION_MM_SET_DEBUG_INFO,
33 ION_MM_GET_DEBUG_INFO,
34 ION_MM_SET_SF_BUF_INFO,
35 ION_MM_GET_SF_BUF_INFO,
36 ION_MM_CONFIG_BUFFER_EXT
37 };
38
39 enum ION_SYS_CMDS {
40 ION_SYS_CACHE_SYNC,
41 ION_SYS_GET_PHYS,
42 ION_SYS_GET_CLIENT,
43 ION_SYS_SET_HANDLE_BACKTRACE,
44 ION_SYS_SET_CLIENT_NAME,
45 ION_SYS_DMA_OP,
46 };
不同的平臺實現這些方式不一樣,然後根據ion_platform_data表示平臺定義的各種類型的heap數據類型來分配heap,以高通平臺是定義在dts裏面,mtk平臺定義在驅動當中,舉例如下:
742 static struct ion_platform_heap ion_drv_platform_heaps[] = {
743 {
744 .type = ION_HEAP_TYPE_SYSTEM_CONTIG,
745 .id = ION_HEAP_TYPE_SYSTEM_CONTIG,
746 .name = "ion_system_contig_heap",
747 .base = 0,
748 .size = 0,
749 .align = 0,
750 .priv = NULL,
751 },
752 {
753 .type = ION_HEAP_TYPE_MULTIMEDIA,
754 .id = ION_HEAP_TYPE_MULTIMEDIA,
755 .name = "ion_mm_heap",
756 .base = 0,
757 .size = 0,
758 .align = 0,
759 .priv = NULL,
760 },
761 {
762 .type = ION_HEAP_TYPE_MULTIMEDIA,
763 .id = ION_HEAP_TYPE_MULTIMEDIA_FOR_CAMERA,
764 .name = "ion_mm_heap_for_camera",
765 .base = 0,
766 .size = 0,
767 .align = 0,
768 .priv = NULL,
769 },
根據ion_platform_data定義的heap類型然後接下來分配ion heap結構,不同的heap類型代表不同的分配方式:
37 enum ion_heap_type {
38 ION_HEAP_TYPE_SYSTEM, //通過vmalloc分配內存;
39 ION_HEAP_TYPE_SYSTEM_CONTIG, //通過kmalloc分配內存;
40 ION_HEAP_TYPE_CARVEOUT, //在保留內存塊中(reserve memory)分配內存;
41 ION_HEAP_TYPE_CHUNK, //模塊;
42 ION_HEAP_TYPE_DMA,
43 ION_HEAP_TYPE_CUSTOM, //由客戶自己定義
47 ION_NUM_HEAPS = 16,
48 };
mtk平臺又根據heap data存儲的數據對象分爲:
19 enum mtk_ion_heap_type {
20 ION_HEAP_TYPE_MULTIMEDIA = 10,
21 ION_HEAP_TYPE_FB = 11,
22 ION_HEAP_TYPE_MULTIMEDIA_FOR_CAMERA = 12,
23 ION_HEAP_TYPE_MULTIMEDIA_SEC = 13,
24 ION_HEAP_TYPE_MULTIMEDIA_MAP_MVA = 14,
25 ION_HEAP_TYPE_MULTIMEDIA_PA2MVA = 15,
27 };
以ION_HEAP_TYPE_MULTIMEDIA數據類型爲例,heap的創建最後通過ion_mm_heap_create()實現:
//不同type的heap需要不同的method去分配,不過都是用struct ion_heap_ops來表示;
537 static struct ion_heap_ops system_heap_ops = {
538 .allocate = ion_mm_heap_allocate,
539 .free = ion_mm_heap_free,
540 .map_dma = ion_mm_heap_map_dma,//map the memory for dma to a scatterlist;
541 .unmap_dma = ion_mm_heap_unmap_dma,
542 .map_kernel = ion_heap_map_kernel,//map memory to the kernel;
543 .unmap_kernel = ion_heap_unmap_kernel,
544 .map_user = ion_heap_map_user,
545 .phys = ion_mm_heap_phys,//get physical address of a buffer;
546 .shrink = ion_mm_heap_shrink,
547 .page_pool_total = ion_mm_heap_pool_total,
548 };
static const unsigned int orders[] = { 1, 0 }; //兩個內存池,爲別爲2^1k和2^0k;
799 struct ion_heap *ion_mm_heap_create(struct ion_platform_heap *unused)
800 {
801 struct ion_system_heap *heap;
802 int i;
803
804 heap = kzalloc(sizeof(*heap), GFP_KERNEL);
805 if (!heap) {
806 IONMSG("%s kzalloc failed heap is null.\n", __func__);
807 return ERR_PTR(-ENOMEM);
808 }
809 heap->heap.ops = &system_heap_ops;
810 heap->heap.type = ION_HEAP_TYPE_MULTIMEDIA;
811 heap->heap.flags = ION_HEAP_FLAG_DEFER_FREE;
812 heap->pools = kcalloc(num_orders, sizeof(struct ion_page_pool *), GFP_KERNEL);
813 if (!heap->pools)
814 goto err_alloc_pools;
815 heap->cached_pools = kcalloc(num_orders, sizeof(struct ion_page_pool *), GFP_KERNEL);
816 if (!heap->cached_pools) {
817 kfree(heap->pools);
818 goto err_alloc_pools;
819 }
820 //創建兩種大小類型的pool,後面的alloc就會根據order在這裏面分配;
821 for (i = 0; i < num_orders; i++) {
822 struct ion_page_pool *pool;
823 gfp_t gfp_flags = low_order_gfp_flags;
824
825 if (orders[i] > 0)
826 gfp_flags = high_order_gfp_flags;
827
828 if (unused->id == ION_HEAP_TYPE_MULTIMEDIA_FOR_CAMERA)
829 gfp_flags |= __GFP_HIGHMEM | __GFP_MOVABLE;
831 pool = ion_page_pool_create(gfp_flags, orders[i]);//主要初始化這個pool;
832 if (!pool)
833 goto err_create_pool;
834 heap->pools[i] = pool;
835
836 pool = ion_page_pool_create(gfp_flags, orders[i]);
837 if (!pool)
838 goto err_create_pool;
839 heap->cached_pools[i] = pool;
840 }
860 }
169 struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order)
170 {
171 struct ion_page_pool *pool = kmalloc(sizeof(struct ion_page_pool),
172 GFP_KERNEL);
173 if (!pool) {
174 IONMSG("%s kmalloc failed pool is null.\n", __func__);
175 return NULL;
176 }
177 pool->high_count = 0;
178 pool->low_count = 0;
179 INIT_LIST_HEAD(&pool->low_items); //每一個pool都包含了高地址和低地址的雙向鏈表;
180 INIT_LIST_HEAD(&pool->high_items);
181 pool->gfp_mask = gfp_mask | __GFP_COMP;
182 pool->order = order;
183 mutex_init(&pool->mutex);
184 plist_node_init(&pool->list, order);
185
186 return pool;
187 }
(三)添加ION client
內核和用戶空間都會可以創建ion client,用戶空間open ion設備來創建client,MTK封裝了一層mt_ion_open(),最終調用ion_client_create()來創建;區別在與用戶層創建的name是根據pid:
5693 pIon_client = ion_client_create(g_ion_device, "camera_isp");
kernel-4.4/drivers/staging/android/ion/ion.c:
826 struct ion_client *ion_client_create(struct ion_device *dev,
827 const char *name)
828 {
829 struct ion_client *client;
830 struct task_struct *task;
831 struct rb_node **p;
832 struct rb_node *parent = NULL;
833 struct ion_client *entry;
834 pid_t pid;
835
841 get_task_struct(current->group_leader);
842 task_lock(current->group_leader);
843 pid = task_pid_nr(current->group_leader);
848 if (current->group_leader->flags & PF_KTHREAD) {
849 put_task_struct(current->group_leader);
850 task = NULL;
851 } else {
852 task = current->group_leader;
853 }
854 task_unlock(current->group_leader);
855
856 client = kzalloc(sizeof(struct ion_client), GFP_KERNEL);
857 if (!client)
858 goto err_put_task_struct;
859
860 client->dev = dev;
861 client->handles = RB_ROOT;
862 idr_init(&client->idr);
863 mutex_init(&client->lock);
864 client->task = task;
865 client->pid = pid;
866 client->name = kstrdup(name, GFP_KERNEL);
867 if (!client->name)
868 goto err_free_client;
869
870 down_write(&dev->lock);
871 client->display_serial = ion_get_client_serial(&dev->clients, name);
872 client->display_name = kasprintf(
873 GFP_KERNEL, "%s-%d", name, client->display_serial);
874 if (!client->display_name) {
875 up_write(&dev->lock);
876 goto err_free_client_name;
877 }
//把該clinet放到ion device的紅黑樹列表裏面;
878 p = &dev->clients.rb_node;
879 while (*p) {
880 parent = *p;
881 entry = rb_entry(parent, struct ion_client, node);
882
883 if (client < entry)
884 p = &(*p)->rb_left;
885 else if (client > entry)
886 p = &(*p)->rb_right;
887 }
888 rb_link_node(&client->node, parent, p);
889 rb_insert_color(&client->node, &dev->clients);
890
891 client->debug_root = debugfs_create_file(client->display_name, 0664,
892 dev->clients_debug_root,
893 client, &debug_client_fops);
894 if (!client->debug_root) {
895 char buf[256], *path;
896
897 path = dentry_path(dev->clients_debug_root, buf, 256);
898 pr_err("Failed to create client debugfs at %s/%s\n",
899 path, client->display_name);
900 }
901
902 up_write(&dev->lock);
903
904 return client;
905
914 }