Re: [Ikvm-developers] IKVM Compiled DLL and multithreading

[Micle, F. <Mi...@ad...>]

I don't think my last email was quite clear. The 0 contentions case is when I use a pure .NET application. Whenever I use OpenJDK, it looks like the access to the clr.dll is single-threaded.

Florin


From: Micle, Florin [mailto:Mi...@ad...]
Sent: Tuesday, April 15, 2014 6:29 PM
To: Jeroen Frijters; ikv...@li...
Subject: Re: [Ikvm-developers] IKVM Compiled DLL and multithreading

Is the access to the clr.dll from IKVM synchronized? It looks like most of my contentions are in the clr.dll, calls coming from IKVM.OpenJDK.Core.dll. Is the implementation of the OpenJDK synchronized so that only one thread at a time can actually call into the clr.dll? That would basically explain the performance degradation I see with the increased number of threads.

I wrote some simple app that starts a few threads that do a lot of computations and nested loops and they behave as expected. In fact the performance explorer in Visual Studio reports 0 contentions, although obviously clr.dll is heavily used.

Thanks in advance,
Florin


From: Jeroen Frijters [mailto:je...@su...]
Sent: Thursday, April 10, 2014 11:04 AM
To: Micle, Florin; ikv...@li...<mailto:ikv...@li...>
Subject: RE: IKVM Compiled DLL and multithreading

Without actual code I can only guess, but it could be related to synchronization. In HotSpot, synchronization is heavily optimized (because of the brain damaged design of the early days Java collection classes) and .NET synchronization is not very optimized at all.

Regards,
Jeroen

From: Micle, Florin [mailto:Mi...@ad...]
Sent: Thursday, April 10, 2014 17:56
To: ikv...@li...<mailto:ikv...@li...>
Subject: [Ikvm-developers] IKVM Compiled DLL and multithreading

Hello everyone,

I used IKVMC to compile a jar into a .NET DLL. The jar does some intensive math computations, maxing out the CPU core on which the thread runs.

In Java each thread will max out at 12.5% CPU (because I have 8 cores, 100% / 8 = 12.5% max CPU per thread). It works fine if I have one thread or 6.

If I use this in the .NET world, one thread will use 12.5% CPU, 2 threads will use about 11% CPU each, 3 threads about 9%, 4 threads about 7% each. The performance of each thread degrades considerably the more threads I have. Doesn't happen if I use the jar from a java app.

It feels like it's something deep inside the compiled .NET DLL there is some serialization that occurs, some resource contention... no idea... I tried setting the apartment option to MTA when compiling the jar and it didn't make a difference.

Any suggestions would be highly appreciated.

Best Regards,
Florin Micle