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Change-Id: I179a2a4568d581f26b4d55dc521f1db806f74d91 Signed-off-by: Herman Chen <herman.chen@rock-chips.com>
118 lines
6.2 KiB
Plaintext
118 lines
6.2 KiB
Plaintext
MPP task design (2017.4.7)
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================================================================================
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Mpp task is the contain component for transaction with external user in advanced
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mode. The target of advanced mode is to provide flexible, multiple input/output
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content for extension.
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Mpp task has mpp_meta as the rich content carrier. Mpp meta uses KEY and value
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pair for extension. One task can carries multiple data into or out of mpp.
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The typical case is encoder with OSD and motion detection. One task may contain
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OSD buffer, motion detection buffer, frame buffer and stream buffer as input and
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output stream buffer and motion detection buffer with data. And this case can
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also be used on decoder if decoder wants to output some side information.
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Mpp task transaction
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================================================================================
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1. Mpp task queue
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Mpp task queue is the manager of tasks. Due to user may incorrectly use the task
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we choose the design that hold all task inside mpp. Task queue will create and
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release task. But task queue will not interact with user directly. We use port
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and task status to control the transaction.
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2. Mpp port
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Mpp port is the transaction interface of task queue. External user and internal
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worker thread will use mpp_port_poll / mpp_port_dequeue / mpp_port_enqueue
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interface to poll / dequeue / enqueue the task task queue. Mpp advanced mode is
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using port to connect external user, interface storage and internal process
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thread. Each task queue has two port: input port and output port. And from a
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global view the task will always flow from input port to output port.
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3. Mpp task status
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There are four status for one task. Mpp use list_head to represent the status.
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INPUT_PORT : Initial status for input port user to dequeue. Or when output port
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successfully enqueue a task then the task is on this status.
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INPUT_HOLD : When input port user successfully dequeue a task then the task is
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on this status.
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OUTPUT_PORT: When input port user successfully enqueue a task then the task is
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on OUTPUT_PORT status. And this task is ready for dequeue from
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output port.
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OUTPUT_HOLD: When output port user successfully dequeue a task then the task is
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on this status.
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4. Mpp task / port transaction
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There are three transaction functions on a port: poll / dequeue / enqueue.
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When port user call the transaction function task will be transfer from one
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status to next status. The status transform flow is unidirectional from input
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port to output port.
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The overall relationship graph of task / port / status is shown below.
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1. task queue
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+------------------------------+
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+----+----+ +--------------+ +----+----+
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| 4 | | 3 | | 2.1 |
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+--------+ dequeue <--+ status <--+ enqueue <---------+
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| | | | INPUT_PORT | | | |
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| +---------+ | | +---------+ |
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+------v-----+ | | +--------------+ | | +------+------+
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| 3 | | 2 | | 2 | | 3 |
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| status | | input | | output | | status |
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| INPUT_HOLD | | port | | port | | OUTPUT_HOLD |
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| | | | | | | |
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+------+-----+ | | +--------------+ | | +------^------+
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| +---------+ | 3 | +---------+ |
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| | 4 | | status | | 2.1 | |
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+--------> enqueue +--> INPUT_PORT +--> dequeue +---------+
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+----+----+ +--------------+ -----+----+
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+------------------------------+
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Mpp task transaction of a complete work flow
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================================================================================
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On advanced mode mpp uses two task queue: input task queue and output task
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queue.
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Input task queue connects input side external user to internal worker thread.
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Output task queue connects internal worker thread to output side external user.
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Then there will be three threads to parallelize internal process and external
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transation. This will maximize mpp efficiency.
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The work flow is demonstrated as below graph.
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+-------------------+ +-------------------+
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| input side user | | output side user |
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+----^---------+----+ +----^---------+----+
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| | | |
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+----+----+----v----+ +----+----+----v----+
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| dequeue | enqueue | | dequeue | enqueue |
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+----^----+----+----+ +----^----+----+----+
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| | | |
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+----+---------+----+ MPP +----+---------v----+
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+---+ input port +-----------+ output port +---+
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| +-------------------+ +-------------------+ |
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| | input task queue | | output task queue | |
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| +-------------------+ +-------------------+ |
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| | output port | | input port | |
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| +----+---------^----+ +----+---------^----+ |
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| | | | | |
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| +----v----+----+----+ +----v----+----+----+ |
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| | dequeue | enqueue | | dequeue | enqueue | |
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| +----+----+----^----+ +----+----+----^----+ |
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| +----v---------+---------------------v---------+----+ |
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| | internal work thread | |
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| +---------------------------------------------------+ |
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+-----------------------------------------------------------+
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