Sharing a JavaScript implementation across realms

Brendan Eich brendan at
Wed Jan 14 10:40:02 PST 2015

SpiderMonkey and Firefox OS people I asked about this just now say the 
problems are not realm-specific, rather worker-specific and 
implementation-specific. Best to catch up with them first and get real 
numbers, attributed to realm and worker separately.


Anne van Kesteren wrote:
> On Wed, Jan 14, 2015 at 1:28 AM, Brendan Eich<brendan at>  wrote:
>> Before we go tl;dr on this topic, how about some data to back up the
>> asserted problem size? Filip gently raised the question. How much memory
>> does a realm cost in top open source engines? Fair question, empirical and
>> (I think) not hard to answer. Burdened malloc/GC heap full cost, not net
>> estimate from source analysis, would be best. Cc'ing Nick, who may already
>> know. Thanks,
> Well, I heard that for e.g. B2G we moved from JavaScript workers to
> C++ threads due to memory constraints. It might well be that this is a
> solvable problem in JavaScript engines with sufficient research, it's
> just at the moment (and in the past) it's been blocking us from doing
> certain things.

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