ActivityManagerService中收集可用内存getMemoryInfo的实现

最新推荐文章于 2024-10-30 22:02:14 发布

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ActivityManagerService的getMemoryInfo方法通过JNI调用android_os_Process_getFreeMemory来获取内存信息，主要依据/proc/meminfo文件，关注MemFree和Cached的总和。这个过程涉及到内存统计、文件读取以及内核数据的解析。

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原型：

ActivityManagerService.java

public void getMemoryInfo(ActivityManager.MemoryInfo outInfo)

---------->Process.getFreeMemory() //Process.java

JNI实现 ------------->android_os_Process_getFreeMemory( ) //android_until_Process.cpp

---------------> open("/proc/meminfo", O_RDONLY);

可见其数据来源于/proc/meminfo文件，该文件包含了有关内存的许多不同类型的统计信息，这里只收集了其中两项的和。即MemFree + Cached

MemTotal: 995092 kB
MemFree: 412324 kB
Buffers: 67372 kB
Cached: 218692 kB
SwapCached: 0 kB
Active: 254272 kB
Inactive: 182248 kB
Active(anon): 150656 kB
Inactive(anon): 304 kB
Active(file): 103616 kB
Inactive(file): 181944 kB
Unevictable: 360 kB
Mlocked: 360 kB
HighTotal: 120836 kB
HighFree: 240 kB
LowTotal: 874256 kB
LowFree: 412084 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 4 kB
Writeback: 0 kB
AnonPages: 150856 kB
Mapped: 131816 kB
Shmem: 348 kB
Slab: 19168 kB
SReclaimable: 9248 kB
SUnreclaim: 9920 kB
KernelStack: 3432 kB
PageTables: 3316 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 497544 kB
Committed_AS: 2186448 kB
VmallocTotal: 122880 kB
VmallocUsed: 64980 kB
VmallocChunk: 18436 kB
DirectMap4k: 24568 kB
DirectMap4M: 884736 kB