From 3e734a1279057bad3858c42943d014700c7c8eba Mon Sep 17 00:00:00 2001 From: 345 Date: Mon, 22 May 2023 17:58:15 +0800 Subject: [PATCH] OOM --- .../OOM.md" | 242 ++++++++++++++++++ 1 file changed, 242 insertions(+) diff --git "a/\346\200\247\350\203\275\344\274\230\345\214\226\347\233\270\345\205\263/OOM.md" "b/\346\200\247\350\203\275\344\274\230\345\214\226\347\233\270\345\205\263/OOM.md" index 1cd95d1..8cbe344 100644 --- "a/\346\200\247\350\203\275\344\274\230\345\214\226\347\233\270\345\205\263/OOM.md" +++ "b/\346\200\247\350\203\275\344\274\230\345\214\226\347\233\270\345\205\263/OOM.md" @@ -132,6 +132,8 @@ manager.memoryClass 我使用的手机内存是 16 g，调用返回的是 256Mb， +> manager.memoryClass 对应 build.prop 中 dalvik.vm.heapgrowthlimit + #### 申请更大的堆内存 ```kotlin @@ -141,6 +143,14 @@ manager.largeMemoryClass 可分配的最大对内存上限，**需要在 manifest 文件中设置 android:largeHeap="true" 方可启用** +> manager.largeMemoryClass 对应 build.prop 中 dalvik.vm.heapsize + +#### Runtime.maxMemory + +获取进程最大可获取的内存上限，等于上面这两个值之一 + + + #### /system/build.prop 该目录是Android内存配置相关的文件，里面保存了系统的内存的限制等数据，执行 adb 命令可看到 Android 配置的内存相关信息： @@ -162,3 +172,235 @@ dalvik.vm.heapsize=256m #所有情况下（包括设置android:largeHeap="true" 未设置android:largeHeap="true"的时候，只要申请的内存超过了heapgrowthlimit就会触发oom，而当设置android:largeHeap="true"的时候，只有内存超过了heapsize才会触发oom。heapsize已经是该应用能申请的最大内存（这里不包括native申请的内存）。 +### OOM 演示 + +#### 堆内存分配失败 + +堆内存分配失败对应的是 /art/runtime/gc/heap.cc ，如下代码 + +```c++ +oid Heap::ThrowOutOfMemoryError(Thread* self, size_t byte_count, AllocatorType allocator_type) { + // If we're in a stack overflow, do not create a new exception. It would require running the + // constructor, which will of course still be in a stack overflow. + if (self->IsHandlingStackOverflow()) { + self->SetException( + Runtime::Current()->GetPreAllocatedOutOfMemoryErrorWhenHandlingStackOverflow()); + return; + } + //.... + std::ostringstream oss; + size_t total_bytes_free = GetFreeMemory(); + oss << "Failed to allocate a " << byte_count << " byte allocation with " << total_bytes_free + << " free bytes and " << PrettySize(GetFreeMemoryUntilOOME()) << " until OOM," + << " target footprint " << target_footprint_.load(std::memory_order_relaxed) + << ", growth limit " + << growth_limit_; + + self->ThrowOutOfMemoryError(oss.str().c_str()); +} +``` + +通过上面的分析，我们也知道系统对每个应用都做了最大内存的约束，超过这个值就会 OOM ，下面通过一段代码来演示一下这种类型的 OOM + +```kotlin +fun testOOM() { + val manager = requireContext().getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager + Timber.e("app maxMemory ${manager.memoryClass} Mb") + Timber.e("large app maxMemory ${manager.largeMemoryClass} Mb") + Timber.e("current app maxMemory ${Runtime.getRuntime().maxMemory() / 1024 / 1024} Mb") + var count = 0 + val list = mutableListOf() + while (true) { + Timber.e("count $count total ${count * 20}") + list.add(ByteArray(1024 * 1024 * 20)) + count++ + } +} +``` + +上面代码中每次申请 20mb，测试分为两种情况， + +1. 未开启 largeHeap: + + ```text + E app maxMemory 256 Mb + E large app maxMemory 512 Mb + E current app maxMemory 256 Mb + E count 0 total 0 + E count 1 total 20 + E count 2 total 40 + E count 3 total 60 + E count 4 total 80 + E count 5 total 100 + E count 6 total 120 + E count 7 total 140 + E count 8 total 160 + E count 9 total 180 + E count 10 total 200 + E count 11 total 220 + E count 12 total 240 + java.lang.OutOfMemoryError: Failed to allocate a 20971536 byte allocation with 12386992 free bytes and 11MB until OOM, target footprint 268435456, growth limit 268435456 + ...... + ``` + + 可以看到一共分配了 12次，在第十二次的时候抛出了异常，显示 分配 20 mb 失败，空闲只有 11 mb， + +2. 开启 largeHeap + + ``` + app maxMemory 256 Mb + large app maxMemory 512 Mb + current app maxMemory 512 Mb + E count 0 total 0 + E count 1 total 20 + E count 2 total 40 + E count 3 total 60 + E count 4 total 80 + E count 5 total 100 + E count 6 total 120 + E count 7 total 140 + E count 8 total 160 + E count 9 total 180 + E count 10 total 200 + E count 11 total 220 + E count 12 total 240 + E count 13 total 260 + E count 14 total 280 + E count 15 total 300 + E count 16 total 320 + E count 17 total 340 + E count 18 total 360 + E count 19 total 380 + E count 20 total 400 + E count 21 total 420 + E count 22 total 440 + E count 23 total 460 + E count 24 total 480 + E count 25 total 500 + FATAL EXCEPTION: main + Process: com.dzl.duanzil, PID: 31874 + java.lang.OutOfMemoryError: Failed to allocate a 20971536 byte allocation with 8127816 free bytes and 7937KB until OOM, target footprint 536870912, growth limit 536870912 + ``` + + 可以看到分配了25 次，可使用的内存也增加到了 512 mb + +#### 创建线程失败 + +线程创建会消耗大量的内存资源，创建的过程涉及 java 层 和 native 层，本质上是在 native 层完成的，对应的是 /art/runtime/thread.cc ，如下代码 + +```c++ +void Thread::CreateNativeThread(JNIEnv* env, jobject java_peer, size_t stack_size, bool is_daemon) { + //........ + env->SetLongField(java_peer, WellKnownClasses::java_lang_Thread_nativePeer, 0); + { + std::string msg(child_jni_env_ext.get() == nullptr ? + StringPrintf("Could not allocate JNI Env: %s", error_msg.c_str()) : + StringPrintf("pthread_create (%s stack) failed: %s", + PrettySize(stack_size).c_str(), strerror(pthread_create_result))); + ScopedObjectAccess soa(env); + soa.Self()->ThrowOutOfMemoryError(msg.c_str()); + } +} +``` + +这里借用网上的一张照片来看一下创建线程的流程 + +2841684743512_.pic + +根据上图可以看到主要有两部分，分别是创建 JNI Env 和 创建线程 + +##### 创建 JNI Env 失败 + +1. FD 溢出导致 JNIEnv 创建失败 + + ```kotlin + E/art: ashmem_create_region failed for 'indirect ref table': Too many open files java.lang.OutOfMemoryError:Could not allocate JNI Env at java.lang.Thread.nativeCreate(Native Method) at java.lang.Thread.start(Thread.java:730) + ``` + +2. 虚拟内存不足导致 JNIEnv 创建失败 + + ```kotlin + E OOM_TEST: create thread : 1104 + W com.demo: Throwing OutOfMemoryError "Could not allocate JNI Env: Failed anonymous mmap(0x0, 8192, 0x3, 0x22, -1, 0): Operation not permitted. See process maps in the log." (VmSize 2865432 kB) + E InputEventSender: Exception dispatching finished signal. + E MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback + MessageQueue-JNI: java.lang.OutOfMemoryError: Could not allocate JNI Env: Failed anonymous mmap(0x0, 8192, 0x3, 0x22, -1, 0): Operation not permitted. See process maps in the log. + E MessageQueue-JNI: at java.lang.Thread.nativeCreate(Native Method) + E MessageQueue-JNI: at java.lang.Thread.start(Thread.java:887) + + E AndroidRuntime: FATAL EXCEPTION: main + E AndroidRuntime: Process: com.demo, PID: 3533 + E AndroidRuntime: java.lang.OutOfMemoryError: Could not allocate JNI Env: Failed anonymous mmap(0x0, 8192, 0x3, 0x22, -1, 0): Operation not permitted. See process maps in the log. + E AndroidRuntime: at java.lang.Thread.nativeCreate(Native Method) + E AndroidRuntime: at java.lang.Thread.start(Thread.java:887) + ``` + +##### 创建线程失败 + +1. 虚拟机内存不足导致失败 + + native 通过 FixStackSize 设置线程大小 + + ```c++ + static size_t FixStackSize(size_t stack_size) { + if (stack_size == 0) { + stack_size = Runtime::Current()->GetDefaultStackSize(); + } + stack_size += 1 * MB; + if (kMemoryToolIsAvailable) { + stack_size = std::max(2 * MB, stack_size); + } if (stack_size < PTHREAD_STACK_MIN) { + stack_size = PTHREAD_STACK_MIN; + } + if (Runtime::Current()->ExplicitStackOverflowChecks()) { + stack_size += GetStackOverflowReservedBytes(kRuntimeISA); + } else { + stack_size += Thread::kStackOverflowImplicitCheckSize + + GetStackOverflowReservedBytes(kRuntimeISA); + } + stack_size = RoundUp(stack_size, kPageSize); + return stack_size; + } + ``` + + ```kotlin + W/libc: pthread_create failed: couldn't allocate 1073152-bytes mapped space: Out of memory + W/tch.crowdsourc: Throwing OutOfMemoryError with VmSize 4191668 kB "pthread_create (1040KB stack) failed: Try again" + java.lang.OutOfMemoryError: pthread_create (1040KB stack) failed: Try again + at java.lang.Thread.nativeCreate(Native Method) + at java.lang.Thread.start(Thread.java:753) + ``` + +2. 线程数量超过限制 + + 用一段简单的代码来测试一下 + + ```kotlin + fun testOOM() { + var count = 0 + while (true) { + val thread = Thread(Runnable { + Thread.sleep(1000000000) + }) + thread.start() + count++ + Timber.e("current thread count $count") + } + } + ``` + + 通过打印日志发现，一共创建了 2473 个线程，当然这些线程都是没有任务的线程，报错信息如下所示 + + ```kotlin + pthread_create failed: couldn't allocate 1085440-bytes mapped space: Out of memory + Throwing OutOfMemoryError "pthread_create (1040KB stack) failed: Try again" (VmSize 4192344 kB) + + FATAL EXCEPTION: main + Process: com.dzl.duanzil, PID: 18085 + java.lang.OutOfMemoryError: pthread_create (1040KB stack) failed: Try again + at java.lang.Thread.nativeCreate(Native Method) + ``` + + + +