有客戶反饋視訊播放一段時間就卡住了，且是必現。從logcat資訊上發現是mediaserver程序異常崩潰了，Log如下：

ABI: 'arm'
pid: 246, tid: 1710, name: DecoderAudio  >>> /system/bin/mediaserver <<<
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
    r0 00000000  r1 89c17780  r2 00001180  r3 00000000
    r4 b79822a0  r5 00001200  r6 89c17704  r7 89c17740
    r8 89
 
c17738  r9 00000000  sl 03598a78  fp 00000000
    ip b64234c8  sp 89c176f8  lr b63eaf75  pc b6a8794c  cpsr 200f0010
    d0  f099f6d8f041f6c2  d1  f108f776f10ef738
    d2  f08af7eff0a6f79c  d3  f0f3f71df0c6f7ef
    d4  f171f601f106f624  d5  f366f728f260f699
    d6  f5a8f7bff45ff779  d7  f676f741f6c2f7d2
    d8  3ef5d867c3ece2a5  d9  412e848000000000
 

    d10 0000000000000000  d11 0000000000000000
    d12 0000000000000000  d13 0000000000000000
    d14 0000000000000000  d15 0000000000000000
    d16 0000000000000000  d17 0000000000000000
    d18 3ff0000000000000  d19 4091780000000000
    d20 be5ae5d13e0705cf  d21 4037f9dcb5112287
    d22 bf2a017308872714  d23 3de5d93a5acfd57c
    d24 3ec71de357b1fe7d  d25 3e21e0e0299e8cc5
    d26 4037f9dcb5112287  d27 40032e4a2a741b9f
    d28 3f895d470d6e9486  d29 3f895d470d6e9486
    d30 3
 
fe797c6a435ce85  d31 400921fb54400000
    scr 68000012

backtrace:
    #00 pc 0001694c  /system/lib/libc.so (memcpy+112)
    #01 pc 00042f71  /system/lib/librkffplayer.so (_ZN7android13RkAudioPlayer10queueAudioEPsix+56)
    #02 pc 0004d509  /system/lib/librkffplayer.so (_ZN7android9FFMPlayer6decodeEPsixxiPv+652)
    #03 pc 0003167f  /system/lib/librkffplayer.so (_ZN12DecoderAudio17SoftDecodeProcessEP8AVPacket+910)
    #04 pc 00030ea9  /system/lib/librkffplayer.so (_ZN12DecoderAudio6decodeEPv+280)
    #05 pc 00034203  /system/lib/librkffplayer.so (_ZN12PlayerThread11startThreadEPv+46)
    #06 pc 000417c7  /system/lib/libc.so (_ZL15__pthread_startPv+30)
    #07 pc 00019313  /system/lib/libc.so (__start_thread+6)

在導致異常的程式碼附近新增LOG確認了是malloc呼叫返回空指標，記憶體分配失敗了，但檢視kmsg並未發現LMK或者OOM出現。

檢視系統limit沒有問題：

root@rk3288:/ # ulimit -Sa
time(cpu-seconds)    unlimited
file(blocks)         unlimited
coredump(blocks)     0
data(KiB)            unlimited
stack(KiB)           8192
lockedmem(KiB)       64
nofiles(descriptors) 1024
processes            10576
sigpending           10576
msgqueue(bytes)      819200
maxnice              40
maxrtprio            0
resident-set(KiB)    unlimited
address-space(KiB)   unlimited

[email protected]:/ # ulimit -Ha
time(cpu-seconds)    unlimited
file(blocks)         unlimited
coredump(blocks)     unlimited
data(KiB)            unlimited
stack(KiB)           unlimited
lockedmem(KiB)       64
nofiles(descriptors) 4096
processes            10576
sigpending           10576
msgqueue(bytes)      819200
maxnice              40
maxrtprio            0
resident-set(KiB)    unlimited
address-space(KiB)   unlimited

再看mediaserver程序，發現它的address-space被限制在1370941585 bytes:

130|[email protected]:/ # cat /proc/4506/limits                                      
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            8388608              unlimited            bytes     
Max core file size        0                    unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             10576                10576                processes 
Max open files            1024                 4096                 files     
Max locked memory         65536                65536                bytes     
Max address space         1370941585           unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       10576                10576                signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         40                   40                   
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us    

通過命令修改程序的limit，重新測試視訊正常:

prlimit 4506 9 -1 -1

google從Android6.0開始，對mediaserver程序的虛擬記憶體大小做出了限制，預設值是系統總記憶體的65%，這在普通的手機及平板等產品上沒有問題，但在一些定製的產品，比如低記憶體的電視盒子，或者是多路視訊同時播放的場景，這些產品在播放視訊時候對記憶體的消耗在系統中佔比可能超過65%，從而觸發limit機制導致記憶體申請失敗。