The struct z_page_frame is marked __packed to avoid extra padding as
such padding may represent significant memory waste when lots of page
frames are used. However this is a bad strategy.
The code contained this somewhat dubious comment and code in
free_page_frame_list_put():
/* The structure is packed, which ensures that this is true */
void *node = pf;
sys_slist_append(&free_page_frame_list, node);
This is bad for many reasons:
- type checking is completely bypassed;
- if the sys_snode_t node member is no longer located at the front of
struct z_page_frame then the code will still compile and possibly run
but be broken with memory corruption as a likely outcome;
- the sys_slist_append() code is completely unaware of the packed
attribute which breaks architectures with alignment restrictions.
Let's improve code efficiency as well as memory usage by removing the
packed attribute and manually packing the flags in the unused virtual
address bits. This way the page frame array remains naturally aligned,
data access becomes optimal and the actual array size gets even smaller.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Utilize a code spell-checking tool to scan for and correct spelling errors
in all files within the doc/build, hardware, kernel, project directory.
Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>
There are several subsystems and boards which require a relatively large
system heap (used by k_malloc()) to function properly. This became even
more notable with the recent introduction of the ACPICA library, which
causes ACPI-using boards to require a system heap of up to several
megabytes in size.
Until now, subsystems and boards have tried to solve this by having
Kconfig overlays which modify the default value of HEAP_MEM_POOL_SIZE.
This works ok, except when applications start explicitly setting values
in their prj.conf files:
$ git grep CONFIG_HEAP_MEM_POOL_SIZE= tests samples|wc -l
157
The vast majority of values set by current sample or test applications
is much too small for subsystems like ACPI, which results in the
application not being able to run on such boards.
To solve this situation, we introduce support for subsystems to specify
their own custom system heap size requirement. Subsystems do
this by defining Kconfig options with the prefix HEAP_MEM_POOL_ADD_SIZE_.
The final value of the system heap is the sum of the custom
minimum requirements, or the value existing HEAP_MEM_POOL_SIZE option,
whichever is greater.
We also introduce a new HEAP_MEM_POOL_IGNORE_MIN Kconfig option which
applications can use to force a lower value than what subsystems have
specficied, however this behavior is disabled by default.
Whenever the minimum is greater than the requested value a CMake warning
will be issued in the build output.
This patch ends up modifying several places outside of kernel code,
since the presence of the system heap is no longer detected using a
non-zero CONFIG_HEAP_MEM_POOL_SIZE value, rather it's now detected using
a new K_HEAP_MEM_POOL_SIZE value that's evaluated at build.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Fix SYS_MEM_BLOCKS_DEFINE_STATIC() description.
Use a "memory blocks allocator" instead of "slab",
which is most probably was copy-pasted from
the previous "slab" chapter by mistake.
Signed-off-by: Andrej Butok <andrey.butok@nxp.com>
Attempting to run the memory slab docs snippets will
result in build issues. This PR is an attempt to fix
those.
Signed-off-by: Andrei Hutanu <andrei.hutanu.i@gmail.com>
Modify the signature of the k_mem_slab_free() function with a new one,
replacing the old void **mem with void *mem as a parameter.
The following function:
void k_mem_slab_free(struct k_mem_slab *slab, void **mem);
has the wrong signature. mem is only used as a regular pointer, so there
is no need to use a double-pointer. The correct signature should be:
void k_mem_slab_free(struct k_mem_slab *slab, void *mem);
The issue with the current signature, although functional, is that it is
extremely confusing. I myself, a veteran Zephyr developer, was confused
by this parameter when looking at it recently.
All in-tree uses of the function have been adapted.
Fixes#61888.
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
The kernel documentation listed the memory management API pages under
two different sections: 'Kernel/Kernel Services' and
'Kernel/Memory Management' -- this creates unnecessary confusion and
makes it hard to look up all supported kernel memory management APIs.
This commit relocates the memory management API pages under
'Kernel/Kernel Services' to 'Kernel/Memory Management' so that all
memory management APIs provided by the kernel are described in one
unified section.
The link to the 'Kernel/Memory Management' index page is still left in
the 'Kernel Services' page because it may still be helpful to look at
it as part of the services provided by the Zephyr kernel -- it is just
more substantial than the rest and deserves more visibility.
Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
Move this section under the kernel and alongside other core and low
level features that are tied to the kernel.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
