Android Camera性能分析 第28讲 Buffer Limit Latency
本讲是 Android Camera性能分析专题 的第28讲,我们介绍CameraServer Buffer Limit Latency,包括如下内容:
- Buffer Limit Latency是什么
- Buffer Limit Latency配置
- Buffer Limit Latency实战
视频在线观看:
- 极客笔记:
https://app5d5waway1614.h5.xiaoeknow.com/p/course/column/p_6252b815e4b01a4851ef948a?type=3
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Buffer Limit Latency是什么
Buffer Limit Latency用于衡量当某路Stream dequeue buffer数量达到producer的最大值后,等待HAL处理的耗时。
什么是numOutstandingBuffers
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已经送给HAL,HAL正在处理,未返回的Buffer数量
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视频讲解演示如何查看每路stream的numOutstandingBuffers
什么是camera_stream::max_buffers
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Camera HAL配置的,在未返回buffer的情况下,最多dequeueBuffer的数量
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视频讲解演示如何查看每路stream HAL配置的最大max_buffers
Buffer Limit Latency配置
Buffer Limit Latency直方图配置
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分成10份(默认值), 间隔为33ms
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static const int32_t kBufferLimitLatencyBinSize = 33; //in ms
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Latency histogram of the wait time for handout buffer count to drop below max_buffers.
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添加Sample的时机
- 当numOutstandingBuffers等于camera_stream::max_buffers时,会等待新的Buffer返回,该Latency衡量的是这个等待时间
Buffer Limit Latency实战
// Wait for new buffer returned back if we are running into the limit.
size_t numOutstandingBuffers = getHandoutOutputBufferCountLocked();
if (numOutstandingBuffers == camera_stream::max_buffers) {ALOGV("%s: Already dequeued max output buffers (%d), wait for next returned one.",__FUNCTION__, camera_stream::max_buffers);nsecs_t waitStart = systemTime(SYSTEM_TIME_MONOTONIC);if (waitBufferTimeout < kWaitForBufferDuration) {waitBufferTimeout = kWaitForBufferDuration;}res = mOutputBufferReturnedSignal.waitRelative(mLock, waitBufferTimeout);nsecs_t waitEnd = systemTime(SYSTEM_TIME_MONOTONIC);mBufferLimitLatency.add(waitStart, waitEnd);if (res != OK) {if (res == TIMED_OUT) {ALOGE("%s: wait for output buffer return timed out after %lldms (max_buffers %d)",__FUNCTION__, waitBufferTimeout / 1000000LL,camera_stream::max_buffers);}return res;}size_t updatedNumOutstandingBuffers = getHandoutOutputBufferCountLocked();if (updatedNumOutstandingBuffers >= numOutstandingBuffers) {ALOGE("%s: outsanding buffer count goes from %zu to %zu, ""getBuffer(s) call must not run in parallel!", __FUNCTION__,numOutstandingBuffers, updatedNumOutstandingBuffers);return INVALID_OPERATION;}
}