net: lwm2m: remove attr_list from obj, obj_inst and res_inst structs
The slist attr_list doesn't scale well when added to the LwM2M object,
object instance and resource instance structures. The goal of a
robust LwM2M client is to let the user create MANY object instances
and these will have many resource instances each. The amount of SRAM
taken up by the attr_lists will only increase over time, regardless
of the actual # of write attribute structures reserved via the
LWM2M_NUM_ATTR config setting.
Instead, let's remove the slist from these structures and add a
reference pointer to the lwm2m_attr structure. We can use this
reference to create the one to many relationship between the objects,
object instances and resource instances for a much smaller amount of
code and SRAM resources.
The sacrifice for these savings will be a larger # of iterations when
looking up assigned write attributes and matching them to their
references. However, due to the # of write attributes current being
handled, the # of iterations during this process is very manageable.
Example flash and SRAM savings when building for nrf52_blenano2:
Before patch:
Memory region Used Size Region Size %age Used
FLASH: 139532 B 512 KB 26.61%
SRAM: 36576 B 64 KB 55.81%
IDT_LIST: 148 B 2 KB 7.23%
After patch:
Memory region Used Size Region Size %age Used
FLASH: 139284 B 512 KB 26.57%
SRAM: 36000 B 64 KB 54.93%
IDT_LIST: 148 B 2 KB 7.23%
Summary: This patch saves ~248 bytes of flash and ~576 bytes of SRAM
for the typical configuration of LwM2M client in Zephyr.
NOTE: these values will vary by architecture.
Signed-off-by: Michael Scott <michael@opensourcefoundries.com>
2 files changed
