Re: time to create / memory footprint of VM
- From: Tobias Oberstein <tobias.oberstein@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Mon, 16 Jul 2012 12:21:21 +0200
Thanks Mike, exactly what I wanted to know.
Am 15.07.2012 13:47, schrieb Mike Pall:
Tobias Oberstein wrote:
Could someone give me a rough estimate on
- time it takes to instantiate a new VM
2 microseconds for lua_open() (no libraries)
30 microseconds for lua_open() + luaL_newstate() (with all default libs)
(On Linux/x64 at 3 GHz)
You can cut down on the overhead if you don't need all libraries.
- the minimal memory footprint of a newly created VM instance
8 KB without any libraries
23 KB with all libraries
That's the minimum footprint with a shared allocator across all
instances (i.e. the system allocator, not the builtin one).
Those numbers are really great and very competitive, even when compared
to a run-time/language that was written to optimize those metrics (Erlang).
Say I have a process creating 10k VMs. How long will it take, how
much memory consume?
That's not a useful scale for VM instances. Use one VM for each
thread and divide them up with coroutines. Each coroutines needs
only around 400 bytes, including a minimal stack.
Sure, there is coroutines and deferred patterns. I was just curious
whether the Erlang approach (concurrent sequential state machines
communicating via message passing) would work with LuJIT in principle.
Have a thread pool size cpu cores, and schedule VM to execute on that.
Compared to coroutines/deferred this has the advantage that state is
really isolated and (in the absence of I/O lib) VMs can be preempted
when running untrusted code.
Anyway, one more related thing: the GC (also the planned new one) does
GC per VM instance .. nothing global .. so I can run concurrent GC :
concrruent in the sense multiple VMs collected in parallel (not
concurrent in the sense within 1 VM), right?
Thanks again,
Tobias
--Mike
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