Delphi XE 中的多线程有哪些新功能？

Question

I have seen some time ago people discussing about the new multithreading in Delphi XE and about the fact that Delphi has some 'native' problems because of the way it implements multithreading. And they were recommending some external libraries to replace the default Delphi multithreading.

Can you point me to some documentation and the most popular multithreading library for Delphi XE? Thanks

Answer 1

[You can set thread name: TThread.NameThreadForDebugging .] (implemented in D2010 as David pointed out)

You can create anonymous thread (a thread that executes anonymous function and doesn't need a TThread descendant object): TThread.CreateAnonymousThread .

Delphi threading frameworks are discussed here:

• Delphi - Threading Frameworks ;
• How Do I Choose Between the Various Ways to do Threading in Delphi?

Answer 2

Also, in addition to what's already been mentioned:

• there's TExternalThread wrapper for external threads (accessible via TThread.CurrentThread class property).
• while debugging in the IDE, you can now freeze and thaw individual threads.
• a lot of new stuff in SyncObjs unit: support for condition variables , TLightweightEvent , TLightweightSemaphore , TSpinLock , TSpinWait ,TInterlocked and more...

Answer 3

I think the "native" issues you are talking about are not related to the way TThread is implemented, but to other aspects of the RTL:

• The memory manager is very fast and well written, but it fails to scale in a linear way when running with a number of concurrent threads on multiple cores;
• Reference-counted types (like string and dynamic arrays ) are implemented with an asm lock opcode to have atomic reference counting (InterlockedDecrement/InterlockedIncrement in x64), which may also scale badly on multi-threaded applications (that is, all cores freezes when this opcode is executed - even if newer CPUs made progress about this, an RCU implementation may scale better).

Those weakness are common to all multi-thread libraries - even OTL will suffer about this . They do exist since very early Delphi versions, and are still there with Delphi XE2. The 64 bit implementation is similar (even slower), and the Mac OS platform shares the very same implementation.

Please see this other SO question about how to write scaling multi-threaded applications in Delphi.

To be honest, both points above will appear only on some very specific kind of applications.

So there is nothing to worry about multi-threading in Delphi, if you know those points, and do not abuse of memory manager calls or string process in your threads.

Answer 4

gabr probably mentioned main new additions. What was left probably is the new overloads for TThread.Synchronize and TThread.Queue which can now execute anonymous methods.

Answer 5

I believe all of newly introduced features were covered already.

For the documentation part, here is an archived copy on classic tutorial book Martin Harvey. Multithreading - The Delphi Way. After reading you will most likely realize what there is no real need for any contributed libraries (except, maybe, the thread pool), remember, frameworks are not simplifying things for you, they also depriving you from the fine-grain control.

Answer 6

TThreadedQueue was introduced in XE.

I find it useful for passing information from worker threads to the main thread or other consumer threads. The last part, having multiple consumer threads, was buggy unfortunately. There was a bug in TMonitor, a class introduced by Delphi 2009, used to synchronize access to the queue in TThreadedQueue.

This has been fixed for XE2. See tthreadedqueue-not-capable-of-multiple-consumers