Memory Use

This page shows memory use for gcoap, and for comparison, libcoap. Values are generated using the samr21-xpro board, with the command:

BOARD=samr21-xpro make info-objsize

Also helpful to show sizes in the executable itself:

arm-none-eabi-nm -Sn -t d gcoap.elf

gcoap with Observe extension

Server-side Observe capability is added in PR #6469.

text	data	bss	Notes
2193	208	1182	gcoap.o -- 2 observers and 2 registrations 1 observer and 1 registration: text 2113, data 164 Before addition of Observe: text 1347, data 116
708	0	0	nanocoap.o
2901	208	1182	Total -- 2 observers and 2 registrations 1 observer and 1 registration: text 2821, data 164

Notes

1. The standard thread stack consumes 1024 B of bss in gcoap.o. We plan to experiment with the stack size to further reduce memory use.
2. Excludes unneeded nanocoap_sock.c, and coap_build_reply(), coap_handle_req(), coap_reply_simple(), and coap_well_known_core_default_handler() from nanocoap.c. Reduces text section by 785 B.

libcoap

libcoap includes more functionality -- client-side Observe as well as Block, more coverage of options like Uri-Query, and generally more detailed handling.

At the same time, libcoap also uses heap space for dynamic allocations.

text	data	bss	Notes
3351	0	1404	net.o
3216	0	0	resource.o
1373	0	0	uri.o
991	168	0	pdu.o
914	0	0	option.o
498	0	0	block.o
366	0	0	async.o
290	1	0	debug.o
156	0	0	coap_list.o
72	0	0	encode.o
50	0	0	hashkey.o
38	0	0	str.o
12	0	0	subscribe.o
11327	169	1404	Total

Notes

1. Compiled using the WITH_POSIX flag.