视频网站移动端,互联网保险的特点,资阳市网站seo,wordpress4.9.6 漏洞背景#xff1a;
android系统开发过程中#xff0c;经常会遇到一些low memory kill的问题#xff0c;在分析这些系统低内存导致被杀问题时候#xff0c;经常因为不好复现而成为一个比较烦恼的阻碍。因为这种低内存问题本身就不属于一种功能操作类型的问题#xff0c;属于…背景
android系统开发过程中经常会遇到一些low memory kill的问题在分析这些系统低内存导致被杀问题时候经常因为不好复现而成为一个比较烦恼的阻碍。因为这种低内存问题本身就不属于一种功能操作类型的问题属于一种系统当前可使用的内存少导致的问题所以分析这类lmk低内存被杀的情况迫切需要一种可以帮助我们复现系统低内存的工具今天马哥就给大家介绍一个内存压力工具mem-pressure详细使用和源码剖析。
mem-pressure工具实战展示
系统的mem-pressure并不是自带集成的需要集成这个mem-pressure工具是需要自己进行额外编译的所以要先进行编译mem-pressure的bin文件后再使用。 编译mem-pressure
testtest:~/aosp15$ make mem-pressurePLATFORM_VERSION_CODENAMEVanillaIceCream
PLATFORM_VERSIONVanillaIceCream
TARGET_PRODUCTsdk_phone64_x86_64
TARGET_BUILD_VARIANTeng
TARGET_ARCHx86_64
TARGET_ARCH_VARIANTx86_64
TARGET_2ND_ARCH_VARIANTx86_64
HOST_OSlinux
HOST_OS_EXTRALinux-5.15.0-130-generic-x86_64-Ubuntu-20.04.3-LTS
HOST_CROSS_OSwindows
BUILD_IDAP3A.241005.015.A2
OUT_DIRout[100% 6/6 1s remaining] Install: out/target/product/emu64x/system/bin/mem-pressure#### build completed successfully (6 seconds) ####
注意这里可以看到可以成功编译出mem-pressure
然后在push到手机设备上
testtest:~/aosp15$ adb push out/target/product/emu64x/system/bin/mem-pressure /data/local/tmp/
out/target/product/emu64x/system/bin/mem-pressure: 1 file pushed, 0 skipped. 82.2 MB/s (51264 bytes in 0.001s)接下来既可以正常使用mem-pressure
130|emu64x:/data/local/tmp # ./mem-pressure -h
Usage: [OPTIONS]-d N: Duration in microsecond to sleep between each allocation.-i N: Number of iterations to run the alloc process.-o N: The oom_score to set the child process to before alloc.-s N: Number of bytes to allocate in an alloc process loop.
Aborted
可以看到mem-pressure可以设置一些参数 正常使用也可以不带任何的参数都使用默认的
emu64x:/data/local/tmp # ./mem-pressure
Child 0 allocated 5936 MB
Child 1 allocated 5968 MB
可以到执行mem-pressure后有多个子进程在申请5936 MB内存同时看看logcat是否有lowmemorykiller相关打印 源码分析
源码路径 system/extras/alloc-stress/mem-pressure.cpp 完整源码 先看main方法
void usage() {printf(Usage: [OPTIONS]\n\n -d N: Duration in microsecond to sleep between each allocation.\n -i N: Number of iterations to run the alloc process.\n -o N: The oom_score to set the child process to before alloc.\n -s N: Number of bytes to allocate in an alloc process loop.\n);
}int main(int argc, char* argv[]) {pid_t pid;size_t* shared;int c, i 0;size_t duration 1000;int iterations 0;const char* oom_score 899;size_t step_size 2 * 1024 * 1024; // 2 MBsize_t size step_size;while ((c getopt(argc, argv, hi:d:o:s:)) ! -1) {switch (c) {case i:iterations atoi(optarg);break;case d:duration atoi(optarg);break;case o:oom_score optarg;break;case s:step_size atoi(optarg);break;case h:usage();abort();default:abort();}}shared (size_t*)mmap(NULL, sizeof(size_t), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED,0, 0);while (iterations 0 || i iterations) {*shared 0;pid fork();//不断for新的子进程if (!pid) {/* Child */add_pressure(shared, size, step_size, duration, oom_score);//子进程开始添加内存压力这个是核心方法/* Shoud not get here */exit(0);} else {wait(NULL);//主进程一直等待等到子进程内存到达极限死了才会进行往下执行printf(Child %d allocated %zd MB\n, i, *shared / 1024 / 1024);//打印出子进程已经申请了多少内存size *shared / 2;}i;}
}可以总结一下mem-pressure核心如下 1、不断创建新的子进程 2、每个子进程进行相关的内存申请 3、子进程内存达到极限被杀了后会打印出申请的内存值
再看具体是怎么给进程内存加压的
//申请指定内存大小并进行设置为0
void* alloc_set(size_t size) {void* addr NULL;addr malloc(size);if (!addr) {printf(Allocating %zd MB failed\n, size / 1024 / 1024);} else {memset(addr, 0, size);}return addr;
}void add_pressure(size_t* shared, size_t size, size_t step_size, size_t duration,const char* oom_score) {int fd, ret;fd open(/proc/self/oom_score_adj, O_WRONLY);//给进程的oom_score_adj写入相关adj值的文件ret write(fd, oom_score, strlen(oom_score));//写人对应的oom_score到上面文件if (ret 0) {printf(Writing oom_score_adj failed with err %s\n, strerror(errno));}close(fd);if (alloc_set(size)) {*shared size;}
//这里会一直申请内存while (alloc_set(step_size)) {size step_size;*shared size;usleep(duration);//这里会有个延时1000us}
}更多framework技术干货请关注下面“千里马学框架”
