Is there an operating system limit to the number of threads in a process ? A
test program I was writing created approximately 105 threads for a process
( many unused because of some thread pool code ), and an out of memory error
occurred when an attempt was made to create more threads. Since I do not
believe that the application was using much memory compared to the nearly 1
GIG of total virtual memory, I assume that the out of memory exception had
to do with exceeding a thread creation limit for a single process.

"Edward Diener" <(E-Mail Removed)> wrote in message
news:%(E-Mail Removed)...
> Is there an operating system limit to the number of threads in a process ?

No. The limiting factor usually turns out to be memory. Every thread by
_default_ gets a 1MB stack. Sooner or later you run out of contiguous
virtual address space.

I am surprised though that you hit the wall at 105. I have seen native
programs can several hundred more threads before giving up the ghost. I
haven't seen any reports about likely limits under .Net

<aside>
That said, where high performance is required, it is rarely a good idea to
have so many threads if all of them can compete for the processor. On the
native side of things, a thread pool and an I/O completion port scale
better.
</aside>

Regards,
Will

You can set a smaller stack size for your threads maybe that helps.
But in general if you have lots of threads thread pooling is the best
solution.

"Edward Diener" <(E-Mail Removed)> schrieb im Newsbeitrag
news:#(E-Mail Removed)...
> Is there an operating system limit to the number of threads in a process ?
A
> test program I was writing created approximately 105 threads for a process
> ( many unused because of some thread pool code ), and an out of memory
error
> occurred when an attempt was made to create more threads. Since I do not
> believe that the application was using much memory compared to the nearly
1
> GIG of total virtual memory, I assume that the out of memory exception had
> to do with exceeding a thread creation limit for a single process.
>
>

"William DePalo [MVP VC++]" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "Edward Diener" <(E-Mail Removed)> wrote in message
> news:%(E-Mail Removed)...
>> Is there an operating system limit to the number of threads in a process
>> ?
>
> No. The limiting factor usually turns out to be memory. Every thread by
> _default_ gets a 1MB stack. Sooner or later you run out of contiguous
> virtual address space.
>
> I am surprised though that you hit the wall at 105. I have seen native
> programs can several hundred more threads before giving up the ghost. I
> haven't seen any reports about likely limits under .Net

I realized that the number of threads created was closer to 300 rather than
100. Each thread pool was creating 25 threads. I have since corrected the
test program I am running to use a single thread pool rather than the dozen
or so I was previously using, and everything runs fine now. Thanks for your
explanation about each thread using a 1MB stack. That would explain why I
ran out of memory.

>
> <aside>
> That said, where high performance is required, it is rarely a good idea to
> have so many threads if all of them can compete for the processor. On the
> native side of things, a thread pool and an I/O completion port scale
> better.
> </aside>

There was a thread pool but it was encapsulated in a class which I was
instantiating numerous times even though I really only needed one instance
of the class.

Edward,

Are you aware that .NET has a built-in thread pool available. You made
it sound as if you've created your own and that maybe fine if there are
special requirements. I just thought I'd give you a friendly heads-up
in case you were not aware of it.

Brian

Edward Diener wrote:
> I realized that the number of threads created was closer to 300
> rather than 100. Each thread pool was creating 25 threads. I have
> since corrected the test program I am running to use a single
> thread pool rather than the dozen or so I was previously using,
> and everything runs fine now. Thanks for your explanation about
> each thread using a 1MB stack. That would explain why I ran out
> of memory.
>

"Brian Gideon" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Edward,
>
> Are you aware that .NET has a built-in thread pool available. You made
> it sound as if you've created your own and that maybe fine if there are
> special requirements. I just thought I'd give you a friendly heads-up
> in case you were not aware of it.

Yes, I was aware of it and the decision to use another thread pool was not
mine. Thanks, nonetheless for the heads-up.

>
> Brian
>
> Edward Diener wrote:
>> I realized that the number of threads created was closer to 300
>> rather than 100. Each thread pool was creating 25 threads. I have
>> since corrected the test program I am running to use a single
>> thread pool rather than the dozen or so I was previously using,
>> and everything runs fine now. Thanks for your explanation about
>> each thread using a 1MB stack. That would explain why I ran out
>> of memory.
>>
>

"cody" <(E-Mail Removed)> wrote in message
news:eNlYK%(E-Mail Removed)...
> You can set a smaller stack size for your threads maybe that helps.
> But in general if you have lots of threads thread pooling is the best
> solution.

Thanks for the info about setting a smaller stack size. I will look into
this.

>
> "Edward Diener" <(E-Mail Removed)> schrieb im Newsbeitrag
> news:#(E-Mail Removed)...
>> Is there an operating system limit to the number of threads in a process
>> ?
> A
>> test program I was writing created approximately 105 threads for a
>> process
>> ( many unused because of some thread pool code ), and an out of memory
> error
>> occurred when an attempt was made to create more threads. Since I do not
>> believe that the application was using much memory compared to the nearly
> 1
>> GIG of total virtual memory, I assume that the out of memory exception
>> had
>> to do with exceeding a thread creation limit for a single process.
>>
>>
>
>