V8Flags not in effect

[OutOfEastGate]

hi

I used Javert version 4.1.0 and V8 mode

Before initializing V8Runtime, I set some memory parameters in V8Flag to see what happens when the memory limit is exceeded.

V8Flags v8Flags = NodeRuntimeOptions.V8_FLAGS;
v8Flags.setMaxHeapSize(1);
v8Flags.setMaxOldSpaceSize(2);

Then I executed the following code in V8, but it doesn't seem to have taken effect. I would like to ask if it's because of my incorrect usage. let a = [... new Array (9000000).keys()];

Also, I would like to ask if it is possible to support passing such a parameter every time V8Runtime is initialized, instead of a globally effective configuration

[caoccao]

Please try NODE_FLAGS.

[OutOfEastGate]

Can Node_LLAGS take effect in V8 mode? It doesn't take effect after I set it this way

NodeFlags nodeFlags = NodeRuntimeOptions.NODE_FLAGS;
nodeFlags.setCustomFlags(new String[]{"--max-old-space-size=2", "--max-new-space-size=1"});

[caoccao]

Do you think 1 or 2 is realistic?

[OutOfEastGate]

It is indeed unrealistic, but I want to know if this configuration can take effect and what the performance will be like when the memory exceeds the set value

[OutOfEastGate]

I have tried setting it to a different value, but this restriction does not take effect. If some large data operations are performed, it will still cause OOM

[caoccao]

Please leave a repo with the issue.

[OutOfEastGate]

I set V8Flag to the following parameters

V8Flags v8Flags = NodeRuntimeOptions.V8_FLAGS;
v8Flags.setMaxHeapSize(4);
v8Flags.setMaxOldSpaceSize(4);

Then execute the following JS code

let a = [... new Array (100 * 1000 * 1000).keys()];

It can still execute normally, it seems that the memory limit has not taken effect

When I enlarged the array, there was an OOM exception

<--- Last few GCs --->

[13168:0x7f7e781b0000]     3577 ms: Scavenge 814.7 (831.1) -> 798.7 (831.1) MB, pooled: 0 MB, 0.06 / 0.00 ms  (average mu = 0.602, current mu = 0.580) allocation failure; 
[13168:0x7f7e781b0000]     3584 ms: Scavenge 814.7 (831.1) -> 798.7 (831.1) MB, pooled: 0 MB, 0.06 / 0.00 ms  (average mu = 0.602, current mu = 0.580) allocation failure; 

<--- JS stacktrace --->

#
# Fatal error in , line 0
# API fatal error handler returned after process out of memory
#
#
#
#FailureMessage Object: 0x3146fdf30
==== C stack trace ===============================

    0   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c24ecc3 v8::base::debug::StackTrace::StackTrace() + 19
    1   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c25676b v8::platform::(anonymous namespace)::PrintStackTrace() + 27
    2   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c2405b6 V8_Fatal(char const*, ...) + 390
    3   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c261ff5 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, v8::OOMDetails const&) + 741
    4   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c493657 v8::internal::Heap::FatalProcessOutOfMemory(char const*) + 23
    5   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014c8ca56d v8::internal::Runtime_FatalProcessOutOfMemoryInvalidArrayLength(int, unsigned long*, v8::internal::Isolate*) + 29
    6   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014d8f75b6 Builtins_CEntry_Return1_ArgvOnStack_NoBuiltinExit + 54
    7   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014d8b8a48 Builtins_IterableToList + 1864
    8   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014d9f1bae Builtins_CreateArrayFromIterableHandler + 46
    9   libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014d853e5e Builtins_InterpreterEntryTrampoline + 222
    10  libjavet-v8-macos-x86_64.v.4.1.0.dy 0x000000014d853e5e Builtins_InterpreterEntryTrampoline + 222

[caoccao]

Please read this blog. And, please test your setting in real Node.js.