Re: Background thread with lower priority

Hi Jeffry

The blog entry I wrote in 2004 is something I still stand by today. Only one thing has changed which is the number of threads in the threadpool (not 256 anymore), but that doesn't detract from my point that much.

It has two questions and a statement:
Q1. "So if you change the priority of other threads in your app how will they play nicely with the above four?"
Q2. "What will the results be if that happened to be one of your own threads whose priority you lowered?"
S1. "if you are going to be creating threads and changing their priority you must first be sure you understand the above and cater for them in your design"

The first point is about knowing that you have 3 additional threads not under your control. Design for that.

The 2nd point is about the GC running on whatever thread happens to be running (*unlike* the desktop). Unlike the previous point, this has nothing to do with other threads in your app (as others pointed out) but has to be considered at the system as a whole (other threads are also running on the system, as others pointed out).

Once you understand the implications of the above, my statement kicks in: If you know what you are doing, go for it.

Nothing above is controversial. I can potentially be controversial by saying that 99.99% of managed apps out there do not need to lower the priority of any of their threads; in my *personal* opinion.

If you have any further questions regarding my blog entries please feel free to email me. For questions specific to your needs/work, please continue to use this group.

Cheers
Daniel
--
http://www.danielmoth.com/Blog/

"<ctacke/>" <ctacke[@]opennetcf[dot]com> wrote in message news:uJsv08UHHHA.1912@xxxxxxxxxxxxxxxxxxxxxxx
Correct, priority is irrelevent. The GC runs on the thread that attempted the allocation that triggered GC, but the first thing the GC does is suspend all other managed threads in the currently running process, so if GC hap[pens in a worker, the UI still suspends.


--
Chris Tacke
OpenNETCF Consulting
Managed Code in the Embedded World
www.opennetcf.com
--


"Ginny Caughey [MVP]" <ginny.caughey.online@xxxxxxxxxxxxxx> wrote in message news:uJtEEuUHHHA.4056@xxxxxxxxxxxxxxxxxxxxxxx
Thanks for the link. As I read it, since GC occurs on whatever thread is running when GC needs collecting, the thread priority probably wouldn't matter since that thread is running whatever its priority. At least that's the way I hope it works.

--
Ginny Caughey
Device Application Development MVP


"Jeffry van de Vuurst" <jeffry.cwrmobility@xxxxxxxxxxxxxxxxx> wrote in message news:uicqdLUHHHA.1240@xxxxxxxxxxxxxxxxxxxxxxx
Hi Ginny,

Here's the link: http://www.danielmoth.com/Blog/2004/08/threads-and-threadpriority-with-net.html.

--
Jeffry van de Vuurst
CWR Mobility
www.cwrmobility.com
--
"Ginny Caughey [MVP]" <ginny.caughey.online@xxxxxxxxxxxxxx> wrote in message news:uelq$0THHHA.1252@xxxxxxxxxxxxxxxxxxxxxxx
Jeffrey,

I have desktop apps that run worker threads on lower priorities without problems. I don't happen to have CF apps that do, but I'd suggest just trying it. Do you have a link to Daniel's post? He doesn't usually get things wrong so I should read it.

--
Ginny Caughey
Device Application Development MVP


"Jeffry van de Vuurst" <jeffry.cwrmobility@xxxxxxxxxxxxxxxxx> wrote in message news:%23R9gpwTHHHA.3468@xxxxxxxxxxxxxxxxxxxxxxx
Hi Chris,

Thanks for your reply. I guess my question was not clear enough.

It's not the GC that causes the non-responsiveness. My assumption is that the non-responsiveness is caused by running my background sync on a thread with the same priority as the main thread. So when the background sync starts, both the UI and the sync are competing for the CPU cycles, right?

That's the reason I started creating my own thread and setting the priority lower than the main thread. However, the blog post from Daniel Moth gives me some concerns because it discourages changing the priority of a thread because of unexpected behavior (mentioning the garbage collection). At least, that is my understanding of the article.

So maybe my question should be: is it ok to have a background thread running on a lower priority so not to interfere with the GUI, or does running on lower priority have unexpected side effects (like mentioned in the article) and should be avoided?

Thanks,

--
Jeffry van de Vuurst
CWR Mobility
www.cwrmobility.com
--
"<ctacke/>" <ctacke[@]opennetcf[dot]com> wrote in message news:%23hmTTPTHHHA.2632@xxxxxxxxxxxxxxxxxxxxxxx
If a GC occurs, all threads in the process are suspended. Doesn't matter what priority any of the threads are.

Are you sure it is a GC that's causing the non-responsiveness?


--
Chris Tacke
OpenNETCF Consulting
Managed Code in the Embedded World
www.opennetcf.com
--


"Jeffry van de Vuurst" <jeffry.cwrmobility@xxxxxxxxxxxxxxxxx> wrote in message news:eNdHtCTHHHA.4712@xxxxxxxxxxxxxxxxxxxxxxx
Hi,

I have a CF 2.0 app that uses 2 background threads. 1 for polling for a network connection and 1 for performing a background sync.

First I used the OpenNETCF BackgroundWorker for this purpose. However, when performing a background sync the UI became unresponsive. Now I changed it to a regular thead using:
Thread backgroundSyncThread = new Thread(DoBackgroundSync);
backgroundSyncThread.Priority = ThreadPriority.Lowest;
backgroundSyncThread.IsBackground = true;
backgroundSyncThread.Start();

However, I read here http://www.danielmoth.com/Blog/2004/08/threads-and-threadpriority-with-net.html, that chaging the priority of threads may be risky because garbage collection could run on the low priority thread.

It's an article from August 2004 but does mention CF 2.0 beta 1. Does this still apply? And if so, what are other ways to make sure that the (potentially long) running background thread doesn't freeze the UI? Is doing a Thread.Sleep(0) from the worker thread effective? I've read different stories about the effectiveness of Thread.Sleep(0)...

Thanks,

--
Jeffry van de Vuurst
CWR Mobility
www.cwrmobility.com
--















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