V8js

V8 JS Attributes

Describes V8 JS Engine Runtime related attributes.

Attributes:

Key	Stability	Value Type	Description	Example Values
v8js.gc.type		string	The type of garbage collection.	major; minor; incremental (see more)
v8js.heap.space.name		string	The name of the space type of heap memory. [1]	new_space; old_space; code_space (see more)
v8js.resource.type		string	The type of resource keeping the event loop active.	Immediate; TCPServerWrap; TCPWrap (see more)

[1] v8js.heap.space.name: Value can be retrieved from value space_name of v8.getHeapSpaceStatistics(). The set of reported spaces depends on the V8 version the runtime embeds.

v8js.gc.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
incremental	Incremental (Incremental Marking).
major	Major (Mark Sweep Compact).
minor	Minor (Scavenge).
weakcb	Weak Callbacks (Process Weak Callbacks).

v8js.heap.space.name has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
code_large_object_space	Large object space for code objects.
code_space	Code memory space.
large_object_space	Large object memory space.
map_space	Map memory space. [2]
new_large_object_space	Large object space for young-generation objects.
new_space	New memory space.
old_space	Old memory space.
read_only_space	Read-only memory space, holding immutable objects created at startup.
shared_large_object_space	Large object space for shared objects.
shared_space	Memory space for objects shared across isolates (e.g. shared strings and structs).
shared_trusted_large_object_space	Large object space for shared trusted objects.
shared_trusted_space	Shared variant of the trusted memory space.
trusted_large_object_space	Large object space for trusted objects.
trusted_space	Memory space for trusted objects kept outside the V8 sandbox (e.g. bytecode).

[2]: Only reported by Node.js <= 19; V8 merged the map space into the old space in V8 11.x.

v8js.resource.type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
Immediate	Active setImmediate callbacks.
TCPServerWrap	Active TCP Servers.
TCPWrap	Active TCP connections.
Timeout	Active setTimeout or setInterval timers.
TTYWrap	Active Terminal I/O (stdin/stdout).