安卓内存泄露之DMA-BUF异常增长:Android Studio镜像引起DMA内存泄露 - Wesley's Blog
今天用着安卓 14 的板子的时候突然系统卡死。
查看日志发现launcher都被干掉了
03-04 06:13:35.544 7872 8479 I ActivityManager: vis BFGS 18740: com.android.launcher3 (pid 8407) service
03-04 06:13:35.544 7872 8479 I ActivityManager: com.android.launcher3/com.android.quickstep.TouchInteractionService<=Proc{8077:com.android.systemui/u0a70}
03-04 06:13:36.155 277 277 I lowmemorykiller: Kill 'com.android.launcher3' (8407), uid 10071, oom_score_adj 100 to free 39504kB rss, 46224kB swap; reason: device is low on swap (91200kB < 199552kB) and thrashing (200%)
看dumpsys meminfo发现DMA-BUF占了3G多（4G设备），应用free ram基本没了。
刚开始以为是scrcpy的问题。后来经调查发现是android studio的屏幕镜像问题。
分析
开机一段时间后
Total RAM: 3,991,080K (status normal)
Free RAM: 1,166,810K ( 124,454K cached pss + 623,088K cached kernel + 419,268K free)
DMA-BUF: 1,477,628K ( 876K mapped + 1,476,752K unmapped)
DMA-BUF Heaps: 1,477,628K
DMA-BUF Heaps pool: 249,088K
GPU: 202,320K
Used RAM: 2,763,593K (1,036,373K used pss + 1,727,220K kernel)
Lost RAM: 195,490K
ZRAM: 72,700K physical used for 215,296K in swap (1,995,536K total swap)
Tuning: 192 (large 512), oom 322,560K, restore limit 107,520K (high-end-gfx)
cat /sys/kernel/dmabuf/buffers/*/size，发现有好多483328字节的 inode
cat /sys/kernel/dmabuf/buffers/*/size | grep 483328 | wc -l
有2957个，计算：2957*483328=1429200896=1.4G，和上面的结果差不多。
随便查看一个inode
roc_rk3588s_pc:/ # lsof | grep -w 7248
c2@1.1-service 543 mediacodec 2553u 0000 0,8 0t0 7248 /dmabuf:system
main 4146 root 5088u 0000 0,8 0t0 7248 /dmabuf:system
main 4146 root 5089u 0000 0,8 0t0 7248 /dmabuf:system
lsof | grep "4146" | grep dmabuf | wc -l
有2958条这样的条目
main 4146 root 5973u 0000 0,8 0t0 7690 /dmabuf:system
和上面的数目一一对应
查看是哪一个程序
roc_rk3588s_pc:/ # cat /proc/543/cmdline
/vendor/bin/hw/android.hardware.media.c2@1.1-service
roc_rk3588s_pc:/ # cat /proc/4146/cmdline
app_process/data/local/tmp/.studiocom.android.tools.screensharing.Main--socket=screen-sharing-agent-8055--flags=16
发现是android studio镜像导致的：应该是因为一直黑屏导致反复申请内存导致DMA-BUF泄露。
关闭Android Studio的Device Mirroring功能后，后面使用设备就正常了。
dmabuf_dump
通过dmabuf_dump命令可以更快地查看异常程序
roc_rk3588s_pc:/ # dmabuf_dump -h
Usage: dmabuf_dump -abh per-process/per-buffer stats
-a show all dma buffers (ion) in big table, buffer x process grid
-b show DMA-BUF per-buffer, per-exporter and per-device statistics
-h show this help
If PID is supplied, the dmabuf information for that process is shown.
Per-buffer DMA-BUF stats do not take an argument.
通过dmabuf_dump就可以查看各个程序DMA-BUF的占用情况（包含程序名字、pid、inode等等）或者加其他参数输出不同结果。
roc_rk3588s_pc:/ # dmabuf_dump 4146
main:4146
Name Rss Pss nr_procs Inode
system 472 kB 472 kB 1 4735
system 472 kB 472 kB 1 4736
system 472 kB 472 kB 1 4737
------------------（省略几千行）----------------
system 472 kB 472 kB 1 7688
system 472 kB 472 kB 1 7689
system 472 kB 472 kB 1 7690
PROCESS TOTAL 1395232 kB 1395232 kB
dmabuf total: 1477628 kB kernel_rss: 82396 kB userspace_rss: 1395232 kB userspace_pss: 1395232 kB
参考
Implement DMABUF and GPU memory accounting in Android 12 | Android Open Source Project