source: rtems-docs/c-user/config/bdbuf.rst @ 1af97ad

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Last change on this file since 1af97ad was 1af97ad, checked in by Sebastian Huber <sebastian.huber@…>, on Mar 9, 2020 at 7:52:24 AM

c-user: Move "Block Device Cache Configuration"

Update #3836.

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Block Device Cache Configuration

This section defines Block Device Cache (bdbuf) related configuration parameters.

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.. index:: CONFIGURE_APPLICATION_NEEDS_LIBBLOCK

CONFIGURE_APPLICATION_NEEDS_LIBBLOCK

CONSTANT:
CONFIGURE_APPLICATION_NEEDS_LIBBLOCK
DATA TYPE:
Boolean feature macro.
RANGE:
Defined or undefined.
DEFAULT VALUE:
This is not defined by default.
DESCRIPTION:
Provides a Block Device Cache configuration.
NOTES:
Each option of the Block Device Cache configuration can be explicitly set by the user with the configuration options below. The Block Device Cache is used for example by the RFS and DOSFS file systems.
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.. index:: CONFIGURE_BDBUF_CACHE_MEMORY_SIZE

CONFIGURE_BDBUF_CACHE_MEMORY_SIZE

CONSTANT:
CONFIGURE_BDBUF_CACHE_MEMORY_SIZE
DATA TYPE:
Unsigned integer (size_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 32768 bytes.
DESCRIPTION:
Size of the cache memory in bytes.
NOTES:
None.
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.. index:: CONFIGURE_BDBUF_BUFFER_MAX_SIZE

CONFIGURE_BDBUF_BUFFER_MAX_SIZE

CONSTANT:
CONFIGURE_BDBUF_BUFFER_MAX_SIZE
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
It must be positive and an integral multiple of the buffer minimum size.
DEFAULT VALUE:
The default value is 4096 bytes.
DESCRIPTION:
Defines the maximum size of a buffer in bytes.
NOTES:
None.
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.. index:: CONFIGURE_BDBUF_BUFFER_MIN_SIZE

CONFIGURE_BDBUF_BUFFER_MIN_SIZE

CONSTANT:
CONFIGURE_BDBUF_BUFFER_MIN_SIZE
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 512 bytes.
DESCRIPTION:
Defines the minimum size of a buffer in bytes.
NOTES:
None.
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.. index:: CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS

CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS

CONSTANT:
CONFIGURE_BDBUF_MAX_READ_AHEAD_BLOCKS
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 0.
DESCRIPTION:
Defines the maximum blocks per read-ahead request.
NOTES:
A value of 0 disables the read-ahead task (default). The read-ahead task will issue speculative read transfers if a sequential access pattern is detected. This can improve the performance on some systems.
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.. index:: CONFIGURE_BDBUF_MAX_WRITE_BLOCKS

CONFIGURE_BDBUF_MAX_WRITE_BLOCKS

CONSTANT:
CONFIGURE_BDBUF_MAX_WRITE_BLOCKS
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 16.
DESCRIPTION:
Defines the maximum blocks per write request.
NOTES:
None.
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.. index:: CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY

CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY

CONSTANT:
CONFIGURE_BDBUF_READ_AHEAD_TASK_PRIORITY
DATA TYPE:
Task priority (rtems_task_priority).
RANGE:
Valid task priority.
DEFAULT VALUE:
The default value is 15.
DESCRIPTION:
Defines the read-ahead task priority.
NOTES:
None.
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.. index:: CONFIGURE_BDBUF_TASK_STACK_SIZE

CONFIGURE_BDBUF_TASK_STACK_SIZE

CONSTANT:
CONFIGURE_BDBUF_TASK_STACK_SIZE
DATA TYPE:
Unsigned integer (size_t).
RANGE:
Zero or positive.
DEFAULT VALUE:
The default value is RTEMS_MINIMUM_STACK_SIZE.
DESCRIPTION:
Defines the task stack size of the Block Device Cache tasks in bytes.
NOTES:
None.
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.. index:: CONFIGURE_SWAPOUT_BLOCK_HOLD

CONFIGURE_SWAPOUT_BLOCK_HOLD

CONSTANT:
CONFIGURE_SWAPOUT_BLOCK_HOLD
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 1000 milliseconds.
DESCRIPTION:
Defines the swapout task maximum block hold time in milliseconds.
NOTES:
None.
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.. index:: CONFIGURE_SWAPOUT_SWAP_PERIOD

CONFIGURE_SWAPOUT_SWAP_PERIOD

CONSTANT:
CONFIGURE_SWAPOUT_SWAP_PERIOD
DATA TYPE:
Unsigned integer (uint32_t).
RANGE:
Positive.
DEFAULT VALUE:
The default value is 250 milliseconds.
DESCRIPTION:
Defines the swapout task swap period in milliseconds.
NOTES:
None.
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.. index:: CONFIGURE_SWAPOUT_TASK_PRIORITY

CONFIGURE_SWAPOUT_TASK_PRIORITY

CONSTANT:
CONFIGURE_SWAPOUT_TASK_PRIORITY
DATA TYPE:
Task priority (rtems_task_priority).
RANGE:
Valid task priority.
DEFAULT VALUE:
The default value is 15.
DESCRIPTION:
Defines the swapout task priority.
NOTES:
None.
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.. index:: CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY

CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY

CONSTANT:
CONFIGURE_SWAPOUT_WORKER_TASK_PRIORITY
DATA TYPE:
Task priority (rtems_task_priority).
RANGE:
Valid task priority.
DEFAULT VALUE:
The default value is 15.
DESCRIPTION:
Defines the swapout worker task priority.
NOTES:
None.
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.. index:: CONFIGURE_SWAPOUT_WORKER_TASKS

CONFIGURE_SWAPOUT_WORKER_TASKS

CONSTANT:
CONFIGURE_SWAPOUT_WORKER_TASKS
DATA TYPE:
Unsigned integer (size_t).
RANGE:
Zero or positive.
DEFAULT VALUE:
The default value is 0.
DESCRIPTION:
Defines the swapout worker task count.
NOTES:
None.
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