Message passing between threads: Java 4 times faster than D

Timon Gehr timon.gehr at
Thu Feb 9 11:44:24 PST 2012

On 02/09/2012 08:27 PM, Sean Kelly wrote:
> On Feb 9, 2012, at 10:14 AM, Marco Leise wrote:
>> Am 09.02.2012, 17:22 Uhr, schrieb dsimcha<dsimcha at>:
>>> I wonder how much it helps to just optimize the GC a little.  How much does the performance gap close when you use DMD 2.058 beta instead of 2.057?  This upcoming release has several new garbage collector optimizations.  If the GC is the bottleneck, then it's not surprising that anything that relies heavily on it is slow because D's GC is still fairly naive.
>> I did some OProfile-ing. The full report is attached, but for simplicity it is without call graph this time. Here is an excerpt:
>> CPU: Core 2, speed 2001 MHz (estimated)
>> Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
>> samples  %        linenr info                 symbol name
>> 13838    18.8416  gcx.d:426                   void* gc.gcx.GC.malloc(ulong, uint, ulong*)
>> 4465      6.0795  gcx.d:2454                  ulong gc.gcx.Gcx.fullcollect(void*)
> One random thing that just occurred to me… if the standard receive pattern is:
> receive((int x) { … });
> There's a good chance that a stack frame is being dynamically allocated for the delegate when it's passed to receive (since I don't believe there's any way to declare the parameters to receive as "scope").  I'll have to check this, and maybe consider changing receive to use alias template parameters instead of normal function parameters?

You can mark an entire tuple as scope without trouble:

void foo(T,S...)(T arg1, scope S args) {...}

Does this improve the run time?

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