ESP32 Forum

Posted: **Mon May 25, 2020 11:50 pm**

I am running low on internal RAM for task stack usage, but I have around 10000 bytes available and want to launch a task with a stack of only 3072 bytes. However, the task creation fails and returns -1 (memory). Any idea why this would happen?

These are the results on which I base my numbers. At the time I try to call task create:
heap_caps_get_free_size(MALLOC_CAP_INTERNAL); 10428
heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL); 9808

Code: Select all

ESP_LOGI(TAG, "Launch special LED test");
if (pdPASS != xTaskCreate(led_test_task,"led v5 test", 3072, NULL, 6, &hTsk_LedTest) )
{
     ESP_LOGE(TAG, "LED test task creation failed");
}

Other info:
IDF is v4.0 release/stable
CONFIG_COMPILER_OPTIMIZATION_LEVEL_RELEASE=y
Project is using WiFI, NimBLE and esp-azure

Build-time size info (which does not include runtime-only heap) is:

Code: Select all

idf.py size-components
Scanning dependencies of target size-components
Total sizes:
 DRAM .data size:   21980 bytes
 DRAM .bss  size:   96464 bytes
Used static DRAM:  118444 bytes (   6136 available, 95.1% used)
Used static IRAM:  121095 bytes (   9977 available, 92.4% used)
      Flash code: 1051803 bytes
    Flash rodata:  304700 bytes
Total image size:~1499578 bytes (.bin may be padded larger)

Posted: **Tue May 26, 2020 4:57 am**

Memory fragmentation? The stack has to be contiguous and there may not be any contiguous chunk of that size.

Posted: **Tue May 26, 2020 12:45 pm**

Memory fragmentation could explain my issue, but I thought that the call to

heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL);

tells me the largest contiguous block that can be obtained (9808) and this should be more than adequate.

Posted: **Wed May 27, 2020 1:41 am**

Hi jsam,

Internal memory (MALLOC_CAP_INTERNAL) on ESP32 covers both DRAM (8-bit capable) and IRAM (32-bit capable only). Stacks have to be allocated as DRAM. It's possible you have enough free internal memory in total, but not enough is 8-bit capable.

You can substitute the calls as follows:

Code: Select all

heap_caps_get_free_size(MALLOC_CAP_INTERNAL|MALLOC_CAP_8BIT);
heap_caps_get_largest_free_block(MALLOC_CAP_INTERNAL|MALLOC_CAP_8BIT);

You're correct that a sufficiently high result from heap_caps_get_largest_free_block() should indicate allocation of this size (or very close to it) will succeed, so this covers the case of heap fragmentation.

Posted: **Wed May 27, 2020 5:23 am**

ESP_Angus, when I add the 8 BIT option as you suggest, it reports just 648 bytes available, so that makes sense.
Thanks for that very useful tip!

ESP32 Forum

Task not launching even with plenty of free internal RAM

Task not launching even with plenty of free internal RAM

Re: Task not launching even with plenty of free internal RAM

Re: Task not launching even with plenty of free internal RAM

Re: Task not launching even with plenty of free internal RAM

Re: Task not launching even with plenty of free internal RAM