On Sun, Nov 6, 2016 at 9:29 PM, Isiah Meadows <[email protected]>
wrote:
> My main focus on this was CPU scheduling and time sharing. Most runtimes
> already shove most outside I/O to another thread, so I wasn't that
> concerned about that. (You could use some indirection and deferral to
> implement cooperative multitasking.)
>
The problem isn't that the platform can't execute this in another thread.
The problem is that you can't write synchronous code anymore to do
synchronous code, this comes at a considerable cost of complexity to
programs.
>
>> Please note that efficiency in scheduling is always a function of how
>> well the scheduler matches the use-case in question. Thus it is important
>> to have a low level concept like coroutines upon which user-code can exist
>> that implements the scheduling. Examples of scheduling problems may include:
>>
>> - wait for user-input arrives (i.e. wait for input)
>>
>>
>> - wait for network actcivity (download or upload) has finished (i.e.
>> wait for xhr)
>> - wait for a WebWorker has finished processing (i.e. wait for
>> worker.postMessage)
>> - wait for GPU activity (i.e. query results, texImage2D, bufferData,
>> shader compile etc.)
>>
>> These could be handled by simply returning a promise. Each thread has its
> own event loop which runs within that thread. So just not doing it
> synchronously would be the solution.
>
Promises are a very bad model to handle cooperative multitasking and
quasi-synchronous code (I believe I don't have to illustrate that).
>
>> - evaluation of a dependency graph
>> - evaluation finite state machines (without resorting to state
>> transition methods)
>> - etc.
>>
>> I believe it would be much better to introduce true coroutines to JS,
>> than to try to introduce preemptive threading.
>>
>
> Cooperative multithreading and coroutines can be done with async
> iterators. When those get standardized, it'll become easy to use
> cooperative multitasking. (I need to make well-known symbols identical
> cross-realm to make it work, though.)
>
> ```js
> export atomic async function *sync(file) {
> while (true) {
> if (await yield) await updateFile(file)
> }
> }
> ```
>
More random line noise atop a broken model of co-routines, isn't going to
fix the lack of proper co-routines (in fact, I think this just exasperates
it).
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