[libcamera-devel,v10,06/19] libcamera: pipeline: simple: Don't rely on bufferCount
diff mbox series

Message ID 20221228223003.2265712-7-paul.elder@ideasonboard.com
State New
Headers show
Series
  • lc-compliance: Add test to queue more requests than hardware depth
Related show

Commit Message

Paul Elder Dec. 28, 2022, 10:29 p.m. UTC 
From: Nícolas F. R. A. Prado <nfraprado@collabora.com>

Currently the simple pipeline handler relies on bufferCount to decide on
the number of buffers to allocate internally when a converter is in use
and for the number of V4L2 buffer slots to reserve. Instead, the number
of internal buffers should be the minimum required by the pipeline to
keep the requests flowing, in order to avoid wasting memory, while the
number of V4L2 buffer slots should be greater than the expected number
of requests queued by the application, in order to avoid thrashing
dmabuf mappings, which would degrade performance.

Stop relying on bufferCount for these numbers and instead set them to
appropriate, and independent, constants.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>

---
Changes in v10:
- rename internalBufferCount and bufferSlotCount to inputBufferCount and
  outputBufferCount, respectively
- remove outputBufferCount from Converter::start() parameter
  - instead, each Converter will decide on their own (how do we like
    this?)

Changes in v9:
- rebased

Changes in v8:
- New
---
 include/libcamera/internal/converter.h        |  2 +-
 .../internal/converter/converter_v4l2_m2m.h   |  4 ++--
 src/libcamera/converter.cpp                   |  2 ++
 .../converter/converter_v4l2_m2m.cpp          | 12 ++++++-----
 src/libcamera/pipeline/simple/simple.cpp      | 21 ++++++++++++++-----
 5 files changed, 28 insertions(+), 13 deletions(-)

Patch
diff mbox series 

diff --git a/include/libcamera/internal/converter.h b/include/libcamera/internal/converter.h
index 834ec5ab..e8a5aeca 100644
--- a/include/libcamera/internal/converter.h
+++ b/include/libcamera/internal/converter.h
@@ -49,7 +49,7 @@  public:
 	virtual int exportBuffers(unsigned int output, unsigned int count,
 				  std::vector<std::unique_ptr<FrameBuffer>> *buffers) = 0;
 
-	virtual int start() = 0;
+	virtual int start(unsigned int inputBufferCount) = 0;
 	virtual void stop() = 0;
 
 	virtual int queueBuffers(FrameBuffer *input,
diff --git a/include/libcamera/internal/converter/converter_v4l2_m2m.h b/include/libcamera/internal/converter/converter_v4l2_m2m.h
index 815916d0..8aedb6df 100644
--- a/include/libcamera/internal/converter/converter_v4l2_m2m.h
+++ b/include/libcamera/internal/converter/converter_v4l2_m2m.h
@@ -50,7 +50,7 @@  public:
 	int exportBuffers(unsigned int ouput, unsigned int count,
 			  std::vector<std::unique_ptr<FrameBuffer>> *buffers);
 
-	int start();
+	int start(unsigned int inputBufferCount);
 	void stop();
 
 	int queueBuffers(FrameBuffer *input,
@@ -69,7 +69,7 @@  private:
 		int exportBuffers(unsigned int count,
 				  std::vector<std::unique_ptr<FrameBuffer>> *buffers);
 
-		int start();
+		int start(unsigned int inputBufferCount);
 		void stop();
 
 		int queueBuffers(FrameBuffer *input, FrameBuffer *output);
diff --git a/src/libcamera/converter.cpp b/src/libcamera/converter.cpp
index 3de39cff..2413424b 100644
--- a/src/libcamera/converter.cpp
+++ b/src/libcamera/converter.cpp
@@ -127,6 +127,8 @@  Converter::~Converter()
 /**
  * \fn Converter::start()
  * \brief Start the converter streaming operation
+ * \param[in] inputBufferCount Number of input buffers that will be used to
+ * move video capture device frames into the converter.
  * \return 0 on success or a negative error code otherwise
  */
 
diff --git a/src/libcamera/converter/converter_v4l2_m2m.cpp b/src/libcamera/converter/converter_v4l2_m2m.cpp
index 2a4d1d99..261c3329 100644
--- a/src/libcamera/converter/converter_v4l2_m2m.cpp
+++ b/src/libcamera/converter/converter_v4l2_m2m.cpp
@@ -107,13 +107,15 @@  int V4L2M2MConverter::Stream::exportBuffers(unsigned int count,
 	return m2m_->capture()->exportBuffers(count, buffers);
 }
 
-int V4L2M2MConverter::Stream::start()
+int V4L2M2MConverter::Stream::start(unsigned int inputBufferCount)
 {
-	int ret = m2m_->output()->importBuffers(inputBufferCount_);
+	static constexpr unsigned int kOutputBufferCount = 16;
+
+	int ret = m2m_->output()->importBuffers(inputBufferCount);
 	if (ret < 0)
 		return ret;
 
-	ret = m2m_->capture()->importBuffers(outputBufferCount_);
+	ret = m2m_->capture()->importBuffers(kOutputBufferCount);
 	if (ret < 0) {
 		stop();
 		return ret;
@@ -373,12 +375,12 @@  int V4L2M2MConverter::exportBuffers(unsigned int output, unsigned int count,
 /**
  * \copydoc libcamera::Converter::start
  */
-int V4L2M2MConverter::start()
+int V4L2M2MConverter::start(unsigned int inputBufferCount)
 {
 	int ret;
 
 	for (Stream &stream : streams_) {
-		ret = stream.start();
+		ret = stream.start(inputBufferCount);
 		if (ret < 0) {
 			stop();
 			return ret;
diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index 6b7c6d5c..64f341e1 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -339,6 +339,7 @@  protected:
 
 private:
 	static constexpr unsigned int kNumInternalBuffers = 3;
+	static constexpr unsigned int kSimpleBufferSlotCount = 16;
 
 	struct EntityData {
 		std::unique_ptr<V4L2VideoDevice> video;
@@ -1232,17 +1233,27 @@  int SimplePipelineHandler::start(Camera *camera, [[maybe_unused]] const ControlL
 		return -EBUSY;
 	}
 
+	/*
+	 * Number of internal buffers that will be used to move video capture
+	 * device frames to the converter.
+	 *
+	 * \todo Make this depend on the driver in use instead of being
+	 * hardcoded. In order to not drop frames, the realtime requirements for
+	 * each device should be checked, so it may not be as simple as just
+	 * using the minimum number of buffers required by the driver.
+	 */
+	static constexpr unsigned int internalBufferCount = 3;
+
 	if (data->useConverter_) {
 		/*
 		 * When using the converter allocate a fixed number of internal
 		 * buffers.
 		 */
-		ret = video->allocateBuffers(kNumInternalBuffers,
+		ret = video->allocateBuffers(internalBufferCount,
 					     &data->converterBuffers_);
 	} else {
-		/* Otherwise, prepare for using buffers from the only stream. */
-		Stream *stream = &data->streams_[0];
-		ret = video->importBuffers(stream->configuration().bufferCount);
+		/* Otherwise, prepare for using buffers. */
+		ret = video->importBuffers(kSimpleBufferSlotCount);
 	}
 	if (ret < 0) {
 		releasePipeline(data);
@@ -1258,7 +1269,7 @@  int SimplePipelineHandler::start(Camera *camera, [[maybe_unused]] const ControlL
 	}
 
 	if (data->useConverter_) {
-		ret = data->converter_->start();
+		ret = data->converter_->start(internalBufferCount);
 		if (ret < 0) {
 			stop(camera);
 			return ret;