Re: [scala-user] Profiling Actor-based server: Lots of time in FJTaskRunner

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Re: [scala-user] Profiling Actor-based server: Lots of time in FJTaskRunner

Meredith Gregory
Erik, Alex, John, et al,

i'm loathe to hijack this thread -- which is a good one -- but the experience with the lock up described below is really just the tip of the iceberg. Unless specific scheduling contracts and semantics can be worked out, a pluggable scheduling architecture is just asking for disaster. Worse, it means that a whole host of compiler support that could be provided to apps that use actor-based concurrency is null and void because those solutions (be they model-checking or types-based) will critically depend on specific ranges of scheduling semantics.

Actors and other higher level concurrency constructs are a major appeal of languages like scala. If they prove themselves to be "not ready for prime time" the impact on perception might not be contained to just that usage of the language.

Best wishes,


On Mon, Mar 2, 2009 at 11:55 AM, Erik Engbrecht <[hidden email]> wrote:
FYI - My work still uses the same scheduler.  I've noticed the FJTaskScheduler2 is sometimes overly aggressive in spawning threads, especially if you have a lot of cores, but last time I poked at that particular piece of code it became too conservative with spawning threads and locked up.
I think it's relatively straight forward to use:
to wrap a java.util.concurrent executor:
...and then you can gain a little more control over the behavior.

On Mon, Mar 2, 2009 at 2:47 PM, Alex Cruise <[hidden email]> wrote:
On 03/02/2009 11:39 AM, John Kalucki wrote:
If I get a moment, I hope to fiddle with the Actor library code in question...

If you have a bit of room to maneuver, you might like to have a look at Erik Engbrecht's recent work on refactoring the actor library (starting with http://erikengbrecht.blogspot.com/2009/01/refactoring-scala-actors.html )



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