native内存泄漏分析
一.摘要
我们在分析内存泄漏时java内存泄漏我们可以集成LeakCanary来进行监控，出现问题时会打印出泄漏时的引用关系，那么我们native内存泄漏时如何分析呢？native内存泄漏我们可以通过malloc_debug工具来进行监控，详细的介绍请参考：
https://android.googlesource.com/platform/bionic/+/master/libc/malloc_debug/README.md
二.如何使用
默认情况下高通的手机已经包含了malloc_debug的代码，具体路径在：bionic/libc/malloc_debug/，下边介绍使用方法：
1.使用dumpsys meminfo --unreachable分析
1.1设置你要监控的进程：
adb shell setprop wrap. '"LIBC_DEBUG_MALLOC_OPTIONS=backtrace"' 例如：
adb shell setprop wrap.com.smartisanos.security '"LIBC_DEBUG_MALLOC_OPTIONS=backtrace"'
adb shell am force-stop com.smartisanos.security1.2重启进程：
设置完属性后需要重启进程，我们先杀死进程adb shell am force-stop
如果之前的设置正常，进程重启后你会发现你进程的父进程并不是zygote64，而是：
sh -c LIBC_DEBUG_MALLOC_OPTIONS=backtrace /system/bin/app_process64 /system/bin --application '--nice-name=com.smartisanos.security' com.android.internal.os.WrapperInit 35 28 'android.app.ActivityThread' '0'这就说明我们设置好了
1.3不断复现你的问题并且抓取分配内存的调用栈：adb shell dumpsys meminfo --unreachable pid | tee app_size.txt
1.4对比你APP 不同native size产生的日志问题，寻找问题
例如:
com.smartisanos.security APP Native Heap: 66696byte 时有如下栈信息：
Unreachable memory
65376 bytes in 1349 unreachable allocations
ABI: 'arm64'
48 bytes unreachable at 75aa29e0b0
and 62832 similar unreachable bytes in 1309 allocations
referencing 1248 unreachable bytes in 26 allocations
first 32 bytes of contents:
75aa29e0b0: 18 67 43 4d 76 00 00 00 00 00 00 00 00 00 00 00 .gCMv...........
75aa29e0c0: 00 00 00 00 00 00 00 00 b0 90 fa ad 75 00 00 00 ............u...
#00 pc 000000000006a4f8 /system/lib64/libc++.so (operator new(unsigned long)+32)
#01 pc 000000000007062c /system/lib64/libhwui.so
#02 pc 0000000000068818 /system/lib64/libhwui.so
#03 pc 000000000006c404 /system/lib64/libhwui.so
#04 pc 0000000000075a84 /system/lib64/libhwui.so (android::uirenderer::renderthread::RenderThread::threadLoop()+340)
#05 pc 00000000000114e8 /system/lib64/libutils.so (android::Thread::_threadLoop(void*)+280)
#06 pc 00000000000ad7ec /system/lib64/libandroid_runtime.so (android::AndroidRuntime::javaThreadShell(void*)+140)
#07 pc 000000000006827c /system/lib64/libc.so
#08 pc 000000000001f550 /system/lib64/libc.so
#09 pc 0000000000000000
com.smartisanos.security APP Native Heap: 66696byte 时有如下栈信息：
Unreachable memory
271152 bytes in 5638 unreachable allocations
ABI: 'arm64'
48 bytes unreachable at 75a70be430
and 261408 similar unreachable bytes in 5446 allocations
referencing 9168 unreachable bytes in 191 allocations
first 32 bytes of contents:
75a70be430: 18 67 43 4d 76 00 00 00 00 00 00 00 00 00 00 00 .gCMv...........
75a70be440: 00 00 00 00 00 00 00 00 b0 90 fa ad 75 00 00 00 ............u...
#00 pc 000000000006a4f8 /system/lib64/libc++.so (operator new(unsigned long)+32)
#01 pc 000000000007062c /system/lib64/libhwui.so
#02 pc 0000000000068818 /system/lib64/libhwui.so
#03 pc 000000000006c404 /system/lib64/libhwui.so
#04 pc 0000000000075a84 /system/lib64/libhwui.so (android::uirenderer::renderthread::RenderThread::threadLoop()+340)
#05 pc 00000000000114e8 /system/lib64/libutils.so (android::Thread::_threadLoop(void*)+280)
#06 pc 00000000000ad7ec /system/lib64/libandroid_runtime.so (android::AndroidRuntime::javaThreadShell(void*)+140)
#07 pc 000000000006827c /system/lib64/libc.so
#08 pc 000000000001f550 /system/lib64/libc.so
#09 pc 0000000000000000 我们发现这个栈是一样的，但是占用的内存越来越大，那么我们直接去这个栈里排查是哪里创建了内存，解析了so得到的行号如下：
Stack Trace:
RELADDR FUNCTION FILE:LINE
000000000006a4f8 operator new(unsigned long)+32 external/libcxxabi/src/cxa_new_delete.cpp:46
000000000007062c android::uirenderer::renderthread::RenderMonitor::addFrame(android::uirenderer::FrameInfo&, std::__1::basic_string, std::__1::allocator > const&)+456 frameworks/base/libs/hwui/renderthread/RenderMonitor.cpp:116
0000000000068818 android::uirenderer::renderthread::CanvasContext::draw()+616 frameworks/base/libs/hwui/renderthread/CanvasContext.cpp:489
000000000006c404 android::uirenderer::renderthread::DrawFrameTask::run()+324 frameworks/base/libs/hwui/renderthread/DrawFrameTask.cpp:114
0000000000075a84 android::uirenderer::renderthread::RenderThread::threadLoop()+340 frameworks/base/libs/hwui/renderthread/RenderThread.cpp:376
00000000000114e8 android::Thread::_threadLoop(void*)+280 system/core/libutils/include/utils/StrongPointer.h:?
00000000000ad7ec android::AndroidRuntime::javaThreadShell(void*)+140 frameworks/base/core/jni/AndroidRuntime.cpp:1256
000000000006827c __pthread_start(void*)+36 bionic/libc/bionic/pthread_create.cpp:226
000000000001f550 __start_thread+68 bionic/libc/bionic/clone.cpp:47 我们可以发现这个内存是在RenderMonitor.cpp的116行申请的，那么我们看下对应的代码：
这里创建了一个MonitorTask对象，我们可以猜到这个对象估计是没有释放，那么我们找找它被释放的地方，我们发现这个对象每次执行完才会被delete：
我们继续找找如果task没有被执行呢？我们看到如下代码：
如果mMonitorTaskQueued为true，mAnimatorTaskQueued为true的时候，那么这个task就不会被delete了，到这里我们也就找到了泄漏的原因，因为这里不符合条件导致task永远不会被delete，那么我们做如下修改：
当不符合条件的时候delete task就好了
2.使用native_heapdump_viewer.py分析
有时候我们用dumpsys meminfo --unreachable打印出来的调用栈并没有什么用，即使内存泄漏了，这里显示的内存大小还是差不多的，那么我们就得用native_heapdump_viewer来分析了，使用方法如下：
1.1复现问题多次dump native内存信息：
adb shell am dumpheap -n 6813 /data/local/tmp/heap_6813.txt // 6813是你进程的pid
1.2解析内存信息：
native_heapdump_viewer.py --symbols /home/pzc/sd/log/giant/417189/6-10/symbols ./heap_6813_109444.txt > heap_109444.txt // symbols一定要对应你的rom
1.3对比解析出来的内存信息：
例如我的两次解析结果对比，com.smartisanos.security native size为：115588byte时的信息：
15241187 33.27% 33.27% 6038 7c73b6e550 /system/lib64/libc.so __start_thread bionic/libc/bionic/clone.cpp:47
15241187 33.27% 100.00% 6038 7c73bb727c /system/lib64/libc.so __pthread_start(void*) bionic/libc/bionic/pthread_create.cpp:226
15141747 33.05% 99.35% 4784 7c744fd7ec /system/lib64/libandroid_runtime.so android::AndroidRuntime::javaThreadShell(void*) frameworks/base/core/jni/AndroidRuntime.cpp:1256
15141747 33.05% 100.00% 4784 7c732e04e8 /system/lib64/libutils.so android::Thread::_threadLoop(void*) system/core/libutils/include/utils/StrongPointer.h:?
15107271 32.97% 99.77% 4672 7c761e7ab8 /system/lib64/libhwui.so android::uirenderer::renderthread::RenderThread::threadLoop() frameworks/base/libs/hwui/renderthread/RenderThread.cpp:376
14977578 32.69% 99.14% 3981 7c761e6ca0 /system/lib64/libhwui.so android::uirenderer::renderthread::SignalingRenderTask::run() frameworks/base/libs/hwui/renderthread/RenderTask.cpp:27
14977578 32.69% 100.00% 3981 7c761e692c /system/lib64/libhwui.so android::uirenderer::renderthread::MethodInvokeRenderTask::run() frameworks/base/libs/hwui/renderthread/RenderTask.h:85
8978727 19.60% 59.95% 2262 7c761e551c /system/lib64/libhwui.so android::uirenderer::renderthread::Bridge_dumpProfileInfo(android::uirenderer::renderthread::dumpProfileInfoArgs*) frameworks/base/libs/hwui/renderthread/RenderProxy.cpp:427
8441856 18.43% 94.02% 2061 7c76202b6c /system/lib64/libhwui.so android::uirenderer::FrameInfoVisualizer::dumpData(int) frameworks/base/libs/hwui/FrameInfoVisualizer.cpp:249
8441856 18.43% 100.00% 2061 7c73bb26cc /system/lib64/libc.so fwrite bionic/libc/upstream-openbsd/lib/libc/stdio/fwrite.c:83
8441856 18.43% 100.00% 2061 7c73bb2198 /system/lib64/libc.so __sfvwrite bionic/libc/upstream-openbsd/lib/libc/stdio/fvwrite.c:60
8441856 18.43% 100.00% 2061 7c73bb46e8 /system/lib64/libc.so __swsetup bionic/libc/upstream-openbsd/lib/libc/stdio/wsetup.c:73
8441856 18.43% 100.00% 2061 7c73bb2a64 /system/lib64/libc.so __smakebuf bionic/libc/upstream-openbsd/lib/libc/stdio/makebuf.c:62com.smartisanos.security native size为：130088byte时的信息：
28115314 48.67% 48.67% 9142 7c73b6e550 /system/lib64/libc.so __start_thread bionic/libc/bionic/clone.cpp:47
28115314 48.67% 100.00% 9142 7c73bb727c /system/lib64/libc.so __pthread_start(void*) bionic/libc/bionic/pthread_create.cpp:226
28012378 48.50% 99.63% 7870 7c744fd7ec /system/lib64/libandroid_runtime.so android::AndroidRuntime::javaThreadShell(void*) frameworks/base/core/jni/AndroidRuntime.cpp:1256
28012378 48.50% 100.00% 7870 7c732e04e8 /system/lib64/libutils.so android::Thread::_threadLoop(void*) system/core/libutils/include/utils/StrongPointer.h:?
27976768 48.43% 99.87% 7750 7c761e7ab8 /system/lib64/libhwui.so android::uirenderer::renderthread::RenderThread::threadLoop() frameworks/base/libs/hwui/renderthread/RenderThread.cpp:376
27850347 48.21% 99.55% 7176 7c761e6ca0 /system/lib64/libhwui.so android::uirenderer::renderthread::SignalingRenderTask::run() frameworks/base/libs/hwui/renderthread/RenderTask.cpp:27
27850347 48.21% 100.00% 7176 7c761e692c /system/lib64/libhwui.so android::uirenderer::renderthread::MethodInvokeRenderTask::run() frameworks/base/libs/hwui/renderthread/RenderTask.h:85
16669534 28.86% 59.85% 4204 7c761e551c /system/lib64/libhwui.so android::uirenderer::renderthread::Bridge_dumpProfileInfo(android::uirenderer::renderthread::dumpProfileInfoArgs*) frameworks/base/libs/hwui/renderthread/RenderProxy.cpp:427
15638528 27.07% 93.82% 3818 7c76202b6c /system/lib64/libhwui.so android::uirenderer::FrameInfoVisualizer::dumpData(int) frameworks/base/libs/hwui/FrameInfoVisualizer.cpp:249
15638528 27.07% 100.00% 3818 7c73bb26cc /system/lib64/libc.so fwrite bionic/libc/upstream-openbsd/lib/libc/stdio/fwrite.c:83
15638528 27.07% 100.00% 3818 7c73bb2198 /system/lib64/libc.so __sfvwrite bionic/libc/upstream-openbsd/lib/libc/stdio/fvwrite.c:60
15638528 27.07% 100.00% 3818 7c73bb46e8 /system/lib64/libc.so __swsetup bionic/libc/upstream-openbsd/lib/libc/stdio/wsetup.c:73
15638528 27.07% 100.00% 3818 7c73bb2a64 /system/lib64/libc.so __smakebuf bionic/libc/upstream-openbsd/lib/libc/stdio/makebuf.c:62我们发现这个栈申请的内存越来越大，然后我们就去排查这个栈的代码，我们发现最好malloc是从
FrameInfoVisualizer.cpp:249这里开始的，这里申请了内存但是并没有释放，这里也没有fclose(file);
查了一下fprintf的资料，大概意思是：
fprintf：写入指定的流（这里会创建内存）
dprintf：写入指定的文件描述符（这个看上去并不会创建内存，而是直接写到fd里）
对比了下Q上的代码发现google也发现了这里有问题，并做了修改：
commit 5a44b4ff74fa7b27963c22249c815aef6225cb8d
Author: John Reck
Date: Mon Nov 13 11:32:39 2017 -0800
Fix leak of FILE* in dumping
Avoid fdopen as fclose, which frees the FILE*, will close
the FD which we don't want. Just normalize on dprintf instead,
and we can add buffering if it turns out to matter at some point
Test: ran 'dumpsys gfxinfo framestats' in a loop while observing PSS
Change-Id: I7808753641aa1055cfdf570c3e017017f11f1dee
感兴趣的同学可以再自行研究一下fprintf和dprintf的区别，这里就不继续介绍了
出现问题的原因：
正常用户不会遇到这个问题，这个只有在dumpsys gfxinfo APP的时候会走到，我们性能监控的工具刚好每隔几秒钟会去dumpsys一次，然后就会一直泄漏，修复方案：
https://android.googlesource.com/platform/frameworks/base/+/47f5c3a234c5c201ef640489af3ff25b5eec6652
三.总结
分析内存泄漏要是没有掌握好调试工具，犹如大海捞针，分析异常的困难，掌握了malloc_debug的使用方法，可以让大家分析native内存泄漏问题的效率也大大的提升～