Hi all,
I created a pull request to solve this problem by directly replacing
mem_aglin with malloc to avoid flash size growth.
https://github.com/apache/nuttx/pull/18427
Regards
anjiahao
________________________________
发件人: 安家豪
发送时间: 2026年2月24日 11:33:35
收件人: Alan C. Assis; [email protected]
主题: 答复: [External Mail]Re: Attempt to reduce needless flash usage
increase
Hi Alan and KR,
Thanks for the detailed analysis and patch.
I've tested your change against breadxavr and several other related AVR
configurations. The results are consistent with your findings. This
flash size increase only manifests in very minimal configs —
specifically those that didn't previously pull in mm_memalign. Once a
config already references memalign through other paths, the linker
includes it regardless, so the penalty becomes invisible.
I agree with your approach of making the heap parameter optional via
Kconfig. The patch looks reasonable and the testing is thorough.
I'd suggest just submitting this as a PR directly on GitHub.
Regards
anjiahao
________________________________
发件人: Alan C. Assis <[email protected]>
发送时间: 2026年2月23日 21:00:07
收件人: [email protected]
抄送: 安家豪
主题: [External Mail]Re: Attempt to reduce needless flash usage increase
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Hi KR,
WOW! Thank you for going deeper in the rabbit hole to find the root
cause of this issue!
Yes, 1400 bytes is not much for a 128KB MCU, but could be a show
stopper for a 32KB MCU (or smaller).
And you are right, Xiaomi is not working with the mainline directly,
they used to work in sync with our mainline, but it changed some time
ago because the cadence to inclusion of their patches wasn't ideal.
This change helped them to move faster, but it resulted in other
issues, since small differences could end-up introducing regressions,
so this is why Matteo (linguini) insisted to them to show a real test
log using the mainline to double check everything was correct. The rest
you know, and that is very sad for NuttX and I think for them as well.
I took a look at your commit and that modification seems good to me.
I'm copying it here so that more people can take a look.
Hi anjiahao, could you please take a look?
BR,
Alan
From 191fee9f98c54238bd1f33293cbd053ca126702e Mon Sep 17 00:00:00 2001
From: Kerogit <[email protected]<mailto:[email protected]>>
Date: Sun, 22 Feb 2026 11:14:07 +0100
Subject: [PATCH] mm/mm_heap: add option to remove optional parameter in
mm_initialize_heap
This patch optionally removes parameter heap from struct
mm_heap_config_s,
based on setting of associated configuration option.
Presence of this parameter causes increase of compiled size while there
is only a single in-tree user of this functionality. The patch
makes this parameter optional and disabled for architectures/boards
with DEFAULT_SMALL set.
How much program memory is saved differs between architectures
and is also based on the overall configuration - biggest part
of the savings comes from linker's ability to eliminate some functions.
The patch was tested by building and running NSH on AVR128DA28
(breadxavr:nsh) and also on Qemu Risc-V (rv-virt:nsh). Ostest
on the latter completed successfully.
Signed-off-by: Kerogit <[email protected]<mailto:[email protected]>>
---
drivers/rptun/Kconfig | 1 +
include/nuttx/mm/mm.h | 2 ++
mm/Kconfig | 12 ++++++++++++
mm/mm_heap/mm_initialize.c | 9 +++++++++
4 files changed, 24 insertions(+)
diff --git a/drivers/rptun/Kconfig b/drivers/rptun/Kconfig
index e10dc044b3..3a36e5513e 100644
--- a/drivers/rptun/Kconfig
+++ b/drivers/rptun/Kconfig
@@ -6,6 +6,7 @@
menuconfig RPTUN
bool "Remote Proc Tunnel Driver Support"
default n
+ depends on !MM_DISABLE_INIT_HEAP_POINTER
select RPMSG_VIRTIO
---help---
RPTUN driver is used for multi-cores' communication.
diff --git a/include/nuttx/mm/mm.h b/include/nuttx/mm/mm.h
index 4f8c928b8e..7b58942114 100644
--- a/include/nuttx/mm/mm.h
+++ b/include/nuttx/mm/mm.h
@@ -191,7 +191,9 @@ struct mm_heap_config_s
* If heap != NULL, means malloc struct mm_heap_s from this heap.
*/
+#ifndef CONFIG_MM_DISABLE_INIT_HEAP_POINTER
FAR struct mm_heap_s *heap;
+#endif
FAR const char *name;
FAR void *start;
size_t size;
diff --git a/mm/Kconfig b/mm/Kconfig
index a5904dd19b..34ccd729df 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -337,6 +337,18 @@ config FS_PROCFS_EXCLUDE_MEMPOOL
default DEFAULT_SMALL
depends on FS_PROCFS && MM_HEAP_MEMPOOL_THRESHOLD > 0
+config MM_DISABLE_INIT_HEAP_POINTER
+ bool "Disable heap parameter in mm_initialize_heap"
+ depends on MM_DEFAULT_MANAGER
+ default DEFAULT_SMALL
+ ---help---
+ This parameter is used to specify caller's heap struct
+ to avoid reserving the heap struct from heap range.
+
+ It is currently needed only by the driver for Remote
+ Proc Tunnel and causes code size increase even if this
+ driver is not in use.
+
source "mm/kasan/Kconfig"
config MM_UBSAN
diff --git a/mm/mm_heap/mm_initialize.c b/mm/mm_heap/mm_initialize.c
index cf111e8d3c..c0d47a17be 100644
--- a/mm/mm_heap/mm_initialize.c
+++ b/mm/mm_heap/mm_initialize.c
@@ -234,14 +234,21 @@ void mm_addregion(FAR struct mm_heap_s *heap, FAR
void *heapstart,
FAR struct mm_heap_s *
mm_initialize_heap(FAR const struct mm_heap_config_s *config)
{
+#ifndef CONFIG_MM_DISABLE_INIT_HEAP_POINTER
FAR struct mm_heap_s *heap = config->heap;
+#else
+ FAR struct mm_heap_s *heap;
+#endif
+
FAR const char *name = config->name;
FAR void *heapstart = config->start;
size_t heapsize = config->size;
int i;
minfo("Heap: name=%s, start=%p size=%zu\n", name, heapstart,
heapsize);
+#ifndef CONFIG_MM_DISABLE_INIT_HEAP_POINTER
if (heap == NULL)
+#endif
{
/* First ensure the memory to be used is aligned */
@@ -257,6 +264,7 @@ mm_initialize_heap(FAR const struct
mm_heap_config_s *config)
DEBUGASSERT(MM_MIN_CHUNK >= MM_SIZEOF_ALLOCNODE);
}
+#ifndef CONFIG_MM_DISABLE_INIT_HEAP_POINTER
else
{
heap = mm_memalign(heap, MM_ALIGN, sizeof(struct mm_heap_s));
@@ -265,6 +273,7 @@ mm_initialize_heap(FAR const struct
mm_heap_config_s *config)
return NULL;
}
}
+#endif
/* Set up global variables */
--
2.43.0
On Mon, Feb 23, 2026 at 9:22 AM
<[email protected]<mailto:[email protected]>> wrote:
Hello,
as I mentioned in my previous message (the request for pull request ;-)
), I noticed flash (program memory) usage increase that happened over
last few months.
I bisected the source code and it pointed at commit
6ed4ea63d8168be30227415ea85ae936ca41bb6f . It adds new parameter to
mm_initialize_heap (renamed from mm_initialize.) Further investigation
showed that the program size increase is caused by the new branch (heap
!= NULL). I verified this by forcing the variable to be NULL, the
branch
was optimized away and linker eliminated mm_memalign and mm_shrinkchunk
from the resulting binary - yielding 1400 bytes of reduced size. This
matched the increase I spotted.
I work with 8bit microcontroller with 128kB program flash, so 1400
bytes
is not an insignificant amount.
I then went to analyze how is this function called, I found these
occurences:
1. drivers/rptun/rptun.c - called with heap parameter set
2. inline function mm_initialize - heap set to NULL
Other than that, mm_initialize_heap is not called directly. Indirectly,
it is either called from mm_initialize_pool, or it replaces this
function via #define (mm_initialize_pool translated to
mm_initialize_heap)
Considering this, I also analyzed how mm_initialize_pool is called, I
found:
1. multiple occurrences in various functions in mm/ directory. These
either call mm_initialize_heap with heap set to NULL, or pass whatever
was given to them through
2. fs/fs_heap.c - sets heap parameter to NULL
3. drivers/pci/pci_epc.c - is not using config parameter at all,
instead
it passes four parameters so it was probably not converted when the
interface changed?
(As a side note - this is the second time this week where I found a
change authored or co-authored by Xiaomi that alters some internal
interface and then converts users of that interface... except some.
Seemingly missing are the ones that are fairly recent additions - the
other one is AVR DA/DB subarchitecture which currently fails to build
with default configuration; proposed fix is in my previous message.
Are they/are you working on some outdated fork of NuttX upstream? Even
more curious is that the broken - at least if I understand that
correctly - file pci_epc.c is also authored by Xiaomi. Anyway, back to
the topic at hand.)
If my research above is correct, then in-tree code has only a single
use
case for the change added by the commit but incurs program memory size
penalty for all users (with varying impact.) In such case, I think this
should be made optional. (This may be up for discussion though - the
memory reduction I achieved is 1400 bytes on AVR but only 400 bytes on
rv-virt. The question is if the code clutter - albeit a small one - is
worth it for one less significant architecture.)
I prepared a patch that eliminates this program memory size increase if
the heap parameter is not actually used by anything. It wraps member
value FAR struct mm_heap_s *heap in struct mm_heap_config_s with
#ifndef
CONFIG_MM_DISABLE_INIT_HEAP_POINTER , a new configuration option which
defaults to DEFAULT_SMALL. The RPTUN driver is made to depends on
!MM_DISABLE_INIT_HEAP_POINTER . Other than that, mm_initialize_heap
adds
multiple #ifndef directives to eliminate code related to heap
parameter.
This approach has two benefits:
1. if more users of the heap parameter are added but not made to depend
on !MM_DISABLE_INIT_HEAP_POINTER, build with DEFAULT_SMALL will fail -
no hidden errors
2. other users of struct mm_heap_config_s use memset to clear it before
use. The heap parameter is not set so no code change is needed for
those
calls
The patch is available in a git repository nuttx.git at
git.kerogit.eu<http://git.kerogit.eu>
accessible through HTTP/S. (Trying to prevent bot traffic by not
posting
the URL in machine-readable form.) The relevant branch is called
mm_init_optional_heap. If someone has the time to look at it and
provide
feedback and/or create pull request on GitHub (I don't have an
account),
it would be greatly appreciated. I think the change is quite trivial to
be reasonably sure that it does not break anything but this is
definitively an area where I only have a vague understanding of the
code
at best.
As of note - I did some tests of the change but there was one thing I
was not able to test - the RPTUN driver itself. Don't have any hardware
to try with and I wasn't even able to compile it for AVR (well, to be
more precise - when I tried, it started downloading things from the web
so I stopped the build.)
Following is for the GitHub PR (if it comes to it)
================
Summary
Make heap parameter of function mm_initialize_heap optional in
mm/mm_heap/mm_initialize.c
Problem:
Parameter heap added in commit 6ed4ea63d8168be30227415ea85ae936ca41bb6f
necessitates call of function mm_memalign which can otherwise be
eliminated from compiled binary on small architectures, namely 8-bit
AVR
DA/DB family. This increases program memory consumption by 1400 bytes
on
that architecture. This parameter is currently only used by RPTUN
driver.
Solution:
Add MM_DISABLE_INIT_HEAP_POINTER configuration option which removes
this
parameter and the associated code, if set
Impact
Users: will be able to use more program memory for their application
code
Build:
- new Kconfig option MM_DISABLE_INIT_HEAP_POINTER, defaults to
DEFAULT_SMALL
- rptun driver depends on !MM_DISABLE_INIT_HEAP_POINTER
Compatibility:
- no functional change for architectures/boards that do not set
DEFAULT_SMALL
- architectures that set DEFAULT_SMALL will be unable to build rptun
driver unless the new option is unset manually
Testing
Test 1
Hardware: AVR128DA28 (NSH build for breadxavr board)
Tests performed:
- build test with the new option unset to verify that code does not
change
- build test with the new option set to verify that the code is
functional
Before the patch:
$ make
Register: nsh
Register: sh
LD: nuttx
Memory region Used Size Region Size %age Used
flash: 51489 B 128 KB 39.28%
sram: 636 B 16 KB 3.88%
eeprom: 0 B 512 B 0.00%
rodata: 592 B 4 KB 14.45%
CP: nuttx.hex
CP: nuttx.asm
$ sha256sum nuttx
818bad0a984a3b75ccd0f138e4bfcfa00264807b9a9d6d16683ea42eac01413d nuttx
After the patch (new option not set)
$ make
LD: nuttx
Memory region Used Size Region Size %age Used
flash: 51489 B 128 KB 39.28%
sram: 636 B 16 KB 3.88%
eeprom: 0 B 512 B 0.00%
rodata: 592 B 4 KB 14.45%
CP: nuttx.hex
CP: nuttx.asm
$ sha256sum nuttx
818bad0a984a3b75ccd0f138e4bfcfa00264807b9a9d6d16683ea42eac01413d nuttx
Result - the patch does not change the compiled binary when the new
configuration option is not enabled
After the patch (new option set)
$ make
LD: nuttx
Memory region Used Size Region Size %age Used
flash: 50079 B 128 KB 38.21%
sram: 636 B 16 KB 3.88%
eeprom: 0 B 512 B 0.00%
rodata: 592 B 4 KB 14.45%
CP: nuttx.hex
CP: nuttx.asm
$ minicom
Welcome to minicom 2.10
OPTIONS: I18n
Port /dev/serial/by-id/usb-FTDI_FT230X_Basic_UART_DU0DQ17J-if00-port0,
16:37:48 [U]
Press CTRL-A Z for help on special keys
NuttShell (NSH) NuttX-12.12.0
nsh> help
help usage: help [-v] [<cmd>]
? help
nsh>
Result - NSH is functional and flash usage is reduced
Test 2
Hardware: building for Risc-V Qemu - rv-virt:nsh
Tests performed:
- build test with the new option unset to verify that code does not
change, run in Qemu, run ostest
- build test with the new option set to verify that code runs
correctly,
run in Qemu, run ostest
Before the patch
$ sha256sum nuttx nuttx.asm
9c68c09fae0effec154957ed0a3b45b9e45879d708c3cd55f15f7be3c07c443d nuttx
146c24fad25f74f923b7398fbce5310adfdb88fc3875ed5127f74c058ebf7c60
nuttx.asm
ostest:
dump_assert_info: Current Version: NuttX 12.12.0 b4242042e1 Feb 22
2026
14:44:13 risc-v
...
ostest_main: Exiting with status 0
After the patch (new option in default state, ie. unset)
$ sha256sum nuttx nuttx.asm
79005fc3be7f240896caa2b03b231254f903705b38bfc1eefeb263da880f7150 nuttx
146c24fad25f74f923b7398fbce5310adfdb88fc3875ed5127f74c058ebf7c60
nuttx.asm
dump_assert_info: Current Version: NuttX 12.12.0 ee396982d7 Feb 22
2026
15:46:21 risc-v
...
ostest_main: Exiting with status 0
Result - the resulting binary does differ but the disassembly does not.
Ostest completes successfully.
After the patch (new option set)
Program size reduced by cca 400 bytes (compared by last instruction's
address in disassembly.)
dump_assert_info: Current Version: NuttX 12.12.0 ee396982d7 Feb 22
2026
16:24:11 risc-v
...
ostest_main: Exiting with status 0
NOTE - RPTUN driver, the only user of the (optionally removed) heap
parameter, was not tested - no access to relevant hardware.
================
Thanks for your time
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