Android libmeminfo

android 10 增加了libmeminfo.so, 用于内存信息的查询,主要通过解析/proc/meminfo文件

源代码位于 system/core/libmeminfo, 代码非常简单没什么好说的

// system/core/libmeminfo/include/meminfo/sysmeminfo.h

class SysMemInfo final {
    // System or Global memory accounting
  public:
    static constexpr const char* kMemTotal = "MemTotal:";
    static constexpr const char* kMemFree = "MemFree:";
    static constexpr const char* kMemBuffers = "Buffers:";
    static constexpr const char* kMemCached = "Cached:";
    static constexpr const char* kMemShmem = "Shmem:";
    static constexpr const char* kMemSlab = "Slab:";
    static constexpr const char* kMemSReclaim = "SReclaimable:";
    static constexpr const char* kMemSUnreclaim = "SUnreclaim:";
    static constexpr const char* kMemSwapTotal = "SwapTotal:";
    static constexpr const char* kMemSwapFree = "SwapFree:";
    static constexpr const char* kMemMapped = "Mapped:";
    static constexpr const char* kMemVmallocUsed = "VmallocUsed:";
    static constexpr const char* kMemPageTables = "PageTables:";
    static constexpr const char* kMemKernelStack = "KernelStack:";

    static constexpr const char* bMemcgUsage="memory.usage_in_bytes";
    static constexpr const char* bMemcgLimit="memory.limit_in_bytes";
    static constexpr const char* bMemcgSwUsage="memory.memsw.usage_in_bytes";
    static constexpr const char* bMemcgSwLimit="memory.memsw.limit_in_bytes";

    static const std::vector<std::string> kDefaultSysMemInfoTags;
    static const std::vector<std::string> kDefaultSysMemcgTags;

    SysMemInfo() = default;

    // Parse /proc/meminfo and read values that are needed
    bool ReadMemInfo(const std::string& path = "/proc/meminfo");
    bool ReadMemInfo(const std::vector<std::string>& tags, std::vector<uint64_t>* out,
                     const std::string& path = "/proc/meminfo");
    bool ReadMemInfo(std::vector<uint64_t>* out, const std::string& path = "/proc/meminfo");

    //bool ReadMemcgInfo(const std::string& path = "/dev/memcg");
    bool ReadMemcgInfo(std::vector<uint64_t>* out, const std::string& path = "/dev/memcg");
    bool ReadMemcgInfo(const std::vector<std::string>& tags, std::vector<uint64_t>* out,
                       const std::string& path = "/dev/memcg");

    ....
}

native中使用方法:

// frameworks/base/core/jni/android_os_Debug.cpp

static void android_os_Debug_getMemInfo(JNIEnv *env, jobject clazz, jlongArray out)
    std::vector<uint64_t> mem(MEMINFO_COUNT);
    std::vector<std::string> tags(::android::meminfo::SysMemInfo::kDefaultSysMemInfoTags);
    tags.insert(tags.begin() + MEMINFO_ZRAM_TOTAL, "Zram:");
    ::android::meminfo::SysMemInfo smi;
    if (!smi.ReadMemInfo(tags, &mem)) {
        jniThrowRuntimeException(env, "SysMemInfo read failed");
        return;
    }
    ...
}

android中接口在 frameworks/base/core/java/com/android/internal/util/MemInfoReader.java中

java中使用,参考 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

MemInfoReader memInfo = new MemInfoReader();
memInfo.readMemInfo();

final long cachedKb = memInfo.getCachedSizeKb();
final long freeKb = memInfo.getFreeSizeKb();
final long zramKb = memInfo.getZramTotalSizeKb();
final long kernelKb = memInfo.getKernelUsedSizeKb();