How Do I Locate a Memory Leak?

[yudaosi]

we have some haps process which use js engine to run the js service.
but we find a process the memory usage increases by 1 MB to 2 MB every day until the memory usage reaches the upper limit set by the JS engine.
Is there any good way to quickly determine whether the JS engine memory leaks and locate which memory leaks? thanks
1934 hap hap 15068 S {on.deviceEngine}

[saghul]

In Debug mode enable leak dumping (see the DUMPLEAKS flag in quickjs.c).

When you exit the interpreter it will print the leaked objects.

[yudaosi]

yeah, I know.
But I have another question. I dump memory usage.
I found that the memory used was far less than the memory malloced, and when I stubbed the test, (The JS object is created in the c native code and then not free.) , It is found that the malloc memory keeps increasing, but the used memory remains unchanged.
What's the reason why these two values are so different?

[saghul]

Not sure I fully understand the question. I wonder if the discrepancy could be due to the inline cache. I'd trust the allocation numbers, since those reflect the calls to our malloc wrappers.

[yudaosi]

oh,ok.
During the walk-through of the memory GC code, we found that the memory GC threshold increases by half after each memory GC.
Will the memory GC be too late or even difficult to trigger the memory GC threshold later? As a result, the memory remains high.
For IoT devices, we hope that the memory can be reclaimed by GC in a timely manner after being used to reduce the memory.

if I set the memory gc threshold 5M at init. After the system runs for a period of time, the memory GC threshold may increase to 20 MB. However, we hope that the maximum memory is less than 20 MB. Normally, the memory usage is about 10 MB. However, the memory GC threshold is high. As a result, the memory is not reclaimed and released. As a result, the memory remains high.

How can I solve this problem? thanks.

[saghul]

You can tune the GC by setting a lower start threshold with JS_SetGCThreshold or by calling JS_RunGC yourself.

[yudaosi]

Thanks for your quick, patient and meticulous answer.

[bnoordhuis]

For IoT devices

@yudaosi out of curiosity, what kind of IoT devices are those?

[yudaosi]

old devices which can not upgrade hardware，only can use 10MB memory