Thanks! > While I understand that this is tempting, please be aware that only one thread may be active in one Isolate at any given time. I was hoping that there could be multiple threads that had "read-only" access to an Isolate's heap - I was looking through how ValueSerializer works and now I understand there's no such thing as "read-only" given the getter/setter functions. However, wondering if this would be possible for simple objects (key/value) and bail for more complex ones. Any other suggestions for how that work can be parallelized, is it even possible? (this is custom serialization, not JSON)
On Wednesday, May 15, 2019 at 11:34:11 AM UTC-7, Jakob Kummerow wrote: > > I'm trying to improve some serialization code in NodeJS and was wondering >> if this could be achieved by going down to the native code and using >> multiple threads to parallelize the serialization of multiple objects. For >> example, imagine we need to serialize 1K objects to JSON/OtherFormat - >> split into 4 x 250 batches and use 4 (non-main) threads to serialize the >> objects, then gather the results and return. >> > > While I understand that this is tempting, please be aware that only one > thread may be active in one Isolate at any given time. Lifting this > restriction would require huge effort, and/or only apply in limited > circumstances (e.g., when an object has a custom toJSON function, you > would have to bail out somehow, because such a function could cause > arbitrary modifications to any other object). > > >> However, I'm having a bit of a hard time understanding a few concepts: >> >> 1. when does the GC kick in for an Isolate? my understanding is that *any >> *V8 code executed in an Isolate can trigger GC for that Isolate - is >> this correct? >> > > Any *allocation* on the managed heap can trigger GC. Of course, when you > don't know what code you're calling (e.g., a user-provided function), then > you have to assume that it might allocate. We use DisallowHeapAllocation > scopes to guard sections where we are sure that no allocation (and hence no > GC) can happen. > > 2. when GC triggers, what happens to pointers that might have been >> extracted from Handle<Object> *and* the Handle is still in scope? >> >> HandleScope scope(isolate); >> Handle<Object> foo = ... >> Object* fooPtr = *foo; >> someCallThatTriggersGC() >> // is fooPtr still valid??? >> > > Raw pointers will become stale, no matter where they came from. So in this > example, fooPtr will be invalid; foo will still be valid (that's the > point of having Handles). > > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-users/183feb94-a4c4-44e6-b881-02d40fa9bd8b%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
