2009/9/10 krovosos <[email protected]>:
>
>
>
>> > we are currently using V8 in a kind of server-side scripting engine.
>> > Javascript is used for implementing business-level logic. V8 is nice,
>> > really! It is fast and well structured. But... Suppose we want to run
>> > a 1000+ small scripts simultaneosly. How can we achieve this? Run
>> > 1000+ processes like Chrome do? Well, not a smart idea. So we have a
>> > single process with 1000+ V8 contexts and there can be only one script
>> > running in V8 at the moment. If it is somehow slow we are stuck,
>> > others are waiting.
>>
>> I appreciate this is annoying, but it's not actually that easy. The
>> contexts are not really independent at the VM level. The
>> single-threaded assumption is in 1000 undocumented places in the code.
>>
>
> Well, isn't that a great adventure - find them all?! Build a better
> structured code? :-)
>
> Ok, just kidding, I understand your point but I was thinking of...
> well...
> Of not 1000 very-local-locks, but 10 not-so-global locks.
> Locks that lock big parts but anyway allow to keep running several
> scripts. All we need is not stopping others forever.
>
> If threads would spend 10% their time waiting
> on those not-so-global-locks that's okay anyway, because they now
> run on 4 CPU instead of 1 (for example).
>
>> Let me suggest some workarounds. I am guessing that you don't have
>> 1000 CPUs. So it might be possible to have one or two V8 processes
>> per CPU, then a load balancer that distributes incoming requests to V8
>> proceses. If you run with preemption support you can switch between
>> V8 threads if one thread gets into a long calculation. If your V8
>> threads are hanging because they are doing long-running IO then you
>> can use the v8::Unlocker class to free up the V8 lock while IO takes
>> place.
>
> Well, several processes is a some sort of solution. But it's not an
> easy solution.
> IPC comes in place, load balancing, something else. It's a solution if
> nothing else helps :-)
>
>
> You are saying that I can do V8::unlock inside the C++ function that
> was called from JS if this C++ function not interfere with V8? Hmm...
>
> That's interesting. I use SQLITE embedded in V8 script and if I can
> run V8 while SQLITE is doing his job it's some sort of optimization...
>
> What if this C++ function has to call another V8 function in turn (so
> the stack is JS-function C++-function JS-function)?
> I need to V8::Lock again before javascript-function call?
Yes, you need a new V8::Locker. Alternating V8::Locker and
V8::Unlockers can be stacked up on the stack.
> void foo()
> {
> v8::Locker locker;
> some_code.Run(); // this javascript code calls cpp_foo ()
> // release lock on destructor call
> }
>
> Handle<Value> cpp_foo(const Arguments& args) // called from V8
> {
> string abc = to_string(args[0]);
>
>
> {
> // okay, since this moment let's forget about V8
> v8::Unlocker unlocker;
> sqlengine.execute(abc);
> } // release unlock on destructor call
>
> // now I can again use V8? And I can run another javascript code?
>
> some_else_code.Run();
>
> }
>
> Is this right?
This all looks right. If you use v8::Locker anywhere you have to use
it everywhere, so the some_else_code.Run() must also be in a
v8::Locker scope.
--
Erik Corry, Software Engineer
Google Denmark ApS. CVR nr. 28 86 69 84
c/o Philip & Partners, 7 Vognmagergade, P.O. Box 2227, DK-1018
Copenhagen K, Denmark.
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