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Unlimited objects information from Chris Johns (ccj@acm.org).

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Joel Sherrill
1999-04-19 17:40:20 +00:00
parent b56206a6ca
commit 338502f1ad
1 changed files with 36 additions and 12 deletions
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48
doc/user/conf.t
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@@ -934,22 +934,46 @@ the workspace area will result in the
directive being invoked with the
@code{@value{RPREFIX}INVALID_ADDRESS} error code.
A worksheet is provided in the Memory Requirements
A worksheet is provided in the @b{Memory Requirements}
chapter of the Applications Supplement document for a specific
target processor to assist the user in calculating the minimum
size of the RTEMS RAM Workspace for each application. The value
calculated with this worksheet is the minimum value that should
be specified as the work_space_size parameter of the
Configuration Table. The user is cautioned that future versions
of RTEMS may not have the same memory requirements per object.
Although the value calculated is sufficient for a particular
target processor and release of RTEMS, memory usage is subject
to change across versions and target processors. The user is
advised to allocate somewhat more memory than the worksheet
recommends to insure compatibility with future releases for a
specific target processor and other target processors. To avoid
problems, the user should recalculate the memory requirements
each time one of the following events occurs:
be specified as the @code{work_space_size} parameter of the
Configuration Table.
The allocation of objects can operate in two modes. The default mode
has an object number ceiling. No more than the specified number of
objects can be allocated from the RTEMS RAM Workspace. The number of objects
specified in the particular API Configuration table fields are
allocated at initialisation. The second mode allows the number of
objects to grow to use the available free memory in the RTEMS RAM Workspace.
The auto-extending mode can be enabled individually for each object
type by using the macro @code{rtems_resource_unlimited}. This takes a value
as a parameter, and is used to set the object maximum number field in
an API Configuration table. The value is an allocation unit size. When
RTEMS is required to grow the object table it is grown by this
size. The kernel will return the object memory back to the RTEMS RAM Workspace
when an object is destroyed. The kernel will only return an allocated
block of objects to the RTEMS RAM Workspace if at least half the allocation
size of free objects remain allocated. RTEMS always keeps one
allocation block of objects allocated. Here is an example of using
@code{rtems_resource_unlimited}:
@example
#define CONFIGURE_MAXIMUM_TASKS rtems_resource_unlimited(5)
@end example
The user is cautioned that future versions of RTEMS may not have the
same memory requirements per object. Although the value calculated is
suficient for a particular target processor and release of RTEMS,
memory usage is subject to change across versions and target
processors. The user is advised to allocate somewhat more memory than
the worksheet recommends to insure compatibility with future releases
for a specific target processor and other target processors. To avoid
problems, the user should recalculate the memory requirements each
time one of the following events occurs:
@itemize @bullet
@item a configuration parameter is modified,