# The Part of Memory Base Libraries

-   [Introduction](#section_introduction)
-   [Architecture](#section_architecture)
-   [Directory Structure](#section_catalogue)
-   [Memory Base Libraries](#section_libraries)
    -   [libdmabufheap system library](#section_libdmabufheap)
    -   [libmeminfo system library (planning)](#section_libmeminfo)
    -   [libmemleak system library (planning)](#section_libmemleak)
    -   [libpurgeable system library (planning)](#section_libpurgeable)
    -   [libspeculative system library (planning)](#section_libspeculative)
-   [Usage Guidelines](#section_usage)
-   [Repositories Involved](#section_projects)

## Introduction<a name="section_introduction"></a>

The part of *Memory base libraries* belongs to the subsystem named *Utils Subsystem*. It provides the system library for upper-layer services to operate memory, ensuring the stability of upper-layer services.

## Architecture<a name="section_architecture"></a>

**Figure  1** Memory Base Libraries architecture

![](figures/en-us_image_fwk.png)

| Memory Base Libraries | User                  |
| -------------- | -------------------------- |
| libdmabufheap  | multimedia service      |
| libmeminfo     | memory manager service         |
| libmemleak     | memory manager service         |
| libpurgeable   | graphic service (planning) |
| libspeculative | system service (planning) |

## Directory Structure<a name="section_catalogue"></a>

```
/utils/memory
├── libdmabufheap           # DMA (Direct Memory Access) memory allocation system library
│   ├── include             # DMA memory allocation system library header directory
│   ├── src                 # DMA memory allocation system library source directory
│   └── test                # DMA memory allocation system library usecase directory
├── libmeminfo              # Memory footprint management library
├── libmemleak              # Memory leak detection library
├── libpurgeable            # Purgeable memory management library
└── libspeculative          # Speculative memory management library
```

## Memory Base Libraries<a name="section_libraries"></a>

*Memory base libraries* is a component of the system library that integrates memory operations and manages them in a unified manner.

### libdmabufheap system library<a name="section_libdmabufheap"></a>

The memory system library provides interfaces for the multimedia service to allocate and share shared memory. By allocating and sharing memory between hardware devices and user space, zero-copy memory between devices and processes is implemented to improve execution efficiency.

### libmeminfo system library (planning)<a name="section_libmeminfo"></a>

It provides interfaces for memory usage queries. It is used for memory footprint query, low memory killing and other scenarios.

### libmemleak system library (planning)<a name="section_libmemleak"></a>

It cooperates with malloc_debug to detect memory leaks of native heap.

### libpurgeable system library (planning)<a name="section_libpurgeable"></a>

It provides management interfaces for discardable-type memory.

### libspeculative system library (planning)<a name="section_libspeculative"></a>

It provides management interfaces for speculative-type memory. It is mainly used by system services for data pre-loading.

## Usage Guidelines<a name="section_usage"></a>

System developers can add or remove this part by configuring the product definition JSON file under **/productdefine/common/products** to enable or disable this part:

` "utils:utils_memory":{} `

## Repositories Involved<a name="section_projects"></a>

[utils](https://gitee.com/openharmony/utils)

# 内存基础库部件

-   [简介](#section_introduction)
-   [部件架构](#section_architecture)
-   [目录](#section_catalogue)
-   [内存基础库](#section_libraries)
    -   [libdmabufheap系统库](#section_libdmabufheap)
    -   [libmeminfo系统库（规划中）](#section_libmeminfo)
    -   [libmemleak系统库（规划中）](#section_libmemleak)
    -   [libpurgeable系统库（规划中）](#section_libpurgeable)
    -   [libspeculative系统库（规划中）](#section_libspeculative)
-   [使用说明](#section_usage)
-   [相关仓](#section_projects)

## 简介<a name="section_introduction"></a>

内存基础库部件位于公共基础库子系统中，为上层业务提供对应的操作内存的系统库，保证上层业务的稳定性。

## 部件架构<a name="section_architecture"></a>

**图1** 内存基础库部件架构图

![](figures/zh-cn_image_fwk.png)

| 内存基础库 | 使用者                  |
| -------------- | -------------------------- |
| libdmabufheap  | 多媒体相关服务      |
| libmeminfo     | 内存管理服务         |
| libmemleak     | 内存管理服务         |
| libpurgeable   | 图形图像相关服务（规划中） |
| libspeculative | 系统服务（规划中） |

## 目录<a name="section_catalogue"></a>

```
/utils/memory
├── libdmabufheap           # DMA (Direct Memory Access) 内存分配链接库
│   ├── include             # DMA内存分配链接库头文件目录
│   ├── src                 # DMA内存分配链接库源代码目录
│   └── test                # DMA内存分配链接库自测用例目录
├── libmeminfo              # 内存占用查询库
├── libmemleak              # 内存泄漏检测库
├── libpurgeable            # 可丢弃类型内存管理库
└── libspeculative          # 投机类型内存管理库
```

## 内存基础库<a name="section_libraries"></a>

内存基础库是集成内存操作的系统库的部件，对内存操作的系统库进行统一管理。

### libdmabufheap系统库<a name="section_libdmabufheap"></a>

为多媒体相关服务提供分配共享内存的接口，通过在硬件设备和用户空间之间分配和共享内存，实现
设备、进程间零拷贝内存，提升执行效率。

### libmeminfo系统库（规划中）<a name="section_libmeminfo"></a>

提供内存占用查询接口，用于内存占用信息查询、低内存查杀等场景。

### libmemleak系统库（规划中）<a name="section_libmemleak"></a>

配合malloc_debug做native heap内存泄漏检测。

### libpurgeable系统库（规划中）<a name="section_libpurgeable"></a>

提供可丢弃类型内存的管理接口。

### libspeculative系统库（规划中）<a name="section_libspeculative"></a>

提供投机类型内存管理接口，用于缓存预读。

## 使用说明<a name="section_usage"></a>

系统开发者可以通过配置productdefine/common/products下的产品定义json文件，增加或移除本部件，来启用或停用本部件。

` "utils:utils_memory":{} `

## 相关仓<a name="section_projects"></a>

[公共基础库子系统](https://gitee.com/openharmony/utils)