I don't think there is a direct way to do this.
There is v8::internal::HeapObject::Size(), but it only gives you a form of
"shallow" size. Under the hood, most (JavaScript-level) objects are
composed of several (heap) objects; e.g. for an Array, all the elements are
stored in a separate backing store, which would not be included in the
result of a ->Size() call on the array itself.
You could try to implement a crawl of the object graph that sums up all the
nested objects, but it's not obvious how you'd deal with shared objects
(canonical example: typically, many objects share the same hidden class.
How do you count the bytes of the hidden class metadata?). DevTools gives
one answer via the "retained size" of each object in a heap snapshot. Does
that serve your needs?
Another way to approximate it is to wrap your function in a pair of gc()
calls, run with --expose-gc --trace-gc, and compare the tracing output
before/after. The limitation is that you only get 0.1 MB resolution; you
can amplify the signal with a loop. Example:
7 ms: Mark-sweep 0.6 (3.7) -> 0.5 (4.7) MB, 1.1 / 0.0 ms
9 ms: Mark-sweep 1.3 (4.7) -> 0.5 (4.7) MB, 1.1 / 0.0 ms
1.3 - 0.5 = 0.8 MB consumed, in this case for 1,000 invocations of function
my_function() { new Array(100); }. The expected value (from knowing what
such an array looks like in memory) is 0.816 MB, so the approximated result
is reasonably accurate.
On Thu, Jul 19, 2018 at 11:43 PM czczcheng <zhecheng2...@yeah.net> wrote:
> Is it possible to get the memory for one of v8::Object ?
> I want to count how much memory was used during a single call of a
> function.
>
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