[dns-sd] Optimize memory usage of SRP client

[Damian-Nordic]

Problem

Current method of allocating data for the SRP services is inefficient, especially once we enable commisionable node advertising for Thread devices which involves both very short and very long TXT entries. In such a case we would allocate N * max(TXT_VALUE_SIZE_i) instead of sum(TXT_VALUE_SIZE_i).

Change overview

Allocate all SRP service data from a single flat buffer instead of using an array of arrays. That way, less memory
is used when entries of the same kind differ in size.
Also, don't duplicate TXT entry keys as they are constants.

Testing

Tested manually using nRF Connect Lock Example. Verified that both operational and commissionable advertising (the latter is not yet enabled by default). work correctly.

Fixes: #8366

[todo]

Switch to max(commissionable TXT key size, operational TXT key size) after optimizing memory usage

connectedhomeip/src/platform/OpenThread/GenericThreadStackManagerImpl_OpenThread.h

Lines 187 to 196 in 0669837

	// TODO: Switch to max(commissionable TXT key size, operational TXT key size) after optimizing memory usage
	static constexpr uint8_t kMaxDnsServiceTxtKeySize = Mdns::OperationalAdvertisingParameters::kTxtMaxKeySize;
	#else
	// Thread only supports operational discovery.
	static constexpr uint8_t kMaxDnsServiceTxtEntriesNumber = Mdns::OperationalAdvertisingParameters::kTxtMaxNumber;
	static constexpr uint8_t kMaxDnsServiceTxtValueSize = Mdns::OperationalAdvertisingParameters::kTxtMaxValueSize;
	static constexpr uint8_t kMaxDnsServiceTxtKeySize = Mdns::OperationalAdvertisingParameters::kTxtMaxKeySize;
	#endif // CHIP_DEVICE_CONFIG_ENABLE_THREAD_COMMISSIONABLE_DISCOVERY
	DnsBrowseCallback mDnsBrowseCallback;

---

This comment was generated by todo based on a TODO comment in 0669837 in #8370. cc @Damian-Nordic.

[github-actions]

Size increase report for "gn_qpg-example-build" from 4ef1ead

File	Section	File	VM
chip-qpg6100-lighting-example.out	.text	32	32
chip-qpg6100-lighting-example.out	.heap	0	8
chip-qpg6100-lighting-example.out	.bss	0	-8

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-qpg6100-lighting-example.out.map and ./pull_artifact/chip-qpg6100-lighting-example.out.map:

BLOAT EXECUTION FAILED WITH CODE 1:
bloaty: unknown file type for file './pull_artifact/chip-qpg6100-lighting-example.out.map'

Comparing ./master_artifact/chip-qpg6100-lighting-example.out and ./pull_artifact/chip-qpg6100-lighting-example.out:

sections,vmsize,filesize
.debug_info,0,3808
.debug_line,0,1207
.debug_str,0,886
.debug_abbrev,0,679
.debug_loc,0,468
.strtab,0,296
.symtab,0,144
.debug_frame,0,140
.debug_aranges,0,64
.debug_ranges,0,64
.text,32,32
.heap,8,0
.bss,-8,0
[Unmapped],0,-32

[github-actions]

Size increase report for "esp32-example-build" from 4ef1ead

File	Section	File	VM
chip-temperature-measurement-app.elf	.flash.text	51	60
chip-all-clusters-app.elf	.flash.text	16	16
chip-lock-app.elf	.flash.text	-64	-64

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize
.debug_str,0,52
.debug_info,0,36
.debug_loc,0,4

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
[Unmapped],0,4045
.debug_info,0,178
.debug_str,0,64
.flash.text,60,51
.debug_loc,0,-2
.debug_line,0,-8

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_info,0,250
.xt.lit._ZN4chip6System5Mutex6UnlockEv,0,128
.xt.lit._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE10_PostEventEPKNS0_15ChipDeviceEventE,0,80
.debug_str,0,59
.xt.prop._ZN4chip11DeviceLayer8Internal26GenericPlatformManagerImplINS0_19PlatformManagerImplEE14_InitChipStackEv,0,40
.flash.text,16,16
.debug_loc,0,-2
.debug_line,0,-7
.xt.prop._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE14_LockChipStackEv,0,-12
.xt.prop._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE15_StartChipTimerEj,0,-12
.xt.prop._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE16_UnlockChipStackEv,0,-12
[Unmapped],0,-16
.xt.lit._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE14_LockChipStackEv,0,-48
.xt.lit._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE15_StartChipTimerEj,0,-48
.xt.lit._ZN4chip11DeviceLayer8Internal35GenericPlatformManagerImpl_FreeRTOSINS0_19PlatformManagerImplEE16_UnlockChipStackEv,0,-48
.xt.prop._ZN4chip6System5Mutex6UnlockEv,0,-108

Comparing ./master_artifact/chip-lock-app.elf and ./pull_artifact/chip-lock-app.elf:

sections,vmsize,filesize
.debug_info,0,266
.debug_str,0,175
[Unmapped],0,64
.debug_loc,0,-2
.debug_line,0,-7
.flash.text,-64,-64

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

[github-actions]

Size increase report for "nrfconnect-example-build" from 4ef1ead

File	Section	File	VM
chip-shell.elf	device_handles	-4	-4
chip-shell.elf	[LOAD #3 [RW]]	0	-23
chip-shell.elf	text	-60	-60
chip-shell.elf	bss	0	-233
chip-lock.elf	[LOAD #3 [RW]]	0	19
chip-lock.elf	device_handles	8	8
chip-lock.elf	text	-56	-56
chip-lock.elf	bss	0	-243

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize
.debug_info,0,3951
.debug_line,0,1059
.debug_str,0,853
.debug_abbrev,0,666
.debug_loc,0,419
.strtab,0,285
.symtab,0,144
.debug_frame,0,140
.debug_aranges,0,64
.debug_ranges,0,8
.shstrtab,0,-1
device_handles,-4,-4
[LOAD #3 [RW]],-23,0
text,-60,-60
bss,-233,0

Comparing ./master_artifact/chip-lock.elf and ./pull_artifact/chip-lock.elf:

sections,vmsize,filesize
.debug_info,0,3924
.debug_line,0,1062
.debug_str,0,853
.debug_abbrev,0,674
.debug_loc,0,427
.strtab,0,296
.symtab,0,144
.debug_frame,0,140
.debug_aranges,0,64
[LOAD #3 [RW]],19,0
.debug_ranges,0,8
device_handles,8,8
text,-56,-56
bss,-243,0