Is there a limit on the number of threads you can create in an
interpreter? Out of no where, I started getting error messages saying
that the interpreter "can't create a thread". The man page did not say
anything on this.

saitology9 <saitology9@gmail.com> wrote:
> Is there a limit on the number of threads you can create in an
> interpreter? Out of no where, I started getting error messages
> saying that the interpreter "can't create a thread". The man page
> did not say anything on this.

Tcl, at least on Linux, seems to impose no limit itself. I tried
creating a huge number not so long ago as a test, and the 'limiting
factor' was the memory consumed by each thread. Eventually the process
would use up all memory in the machine, and become a target for the
Linux OOM killer.

The host OS, however, can enforce a limit if it wants, in which case
Tcl would eventually hit that limit if you create enough threads.

On 8/2/2023 6:26 PM, Rich wrote:
>
> The host OS, however, can enforce a limit if it wants, in which case
> Tcl would eventually hit that limit if you create enough threads.
>

Thanks for the info. This was on Windows 10. It must have been low
memory issue for me.

saitology9 <saitology9@gmail.com> wrote:
> On 8/2/2023 6:26 PM, Rich wrote:
>>
>> The host OS, however, can enforce a limit if it wants, in which case
>> Tcl would eventually hit that limit if you create enough threads.
>>
>
> Thanks for the info. This was on Windows 10. It must have been low
> memory issue for me.

Linux, 1100 empty threads (just thread::create and nothing more), top
reports 12.6g of virtual memory used.

That works out to about 12mb per empty thread.

Naturally if they are doing something they will each be larger.

Rich <rich@example.invalid> writes:

> Linux, 1100 empty threads (just thread::create and nothing more), top
> reports 12.6g of virtual memory used.
>
> That works out to about 12mb per empty thread.

This seems like a lot, so I tested it with an interactive tclsh. After
loading the thread package top shows 5560k. Each thread::create adds
about 1000k. Do you have some other packages loaded in your program?

Joerg

Joerg Mertens <joerg-mertens@t-online.de> wrote:
> Rich <rich@example.invalid> writes:
>
>> Linux, 1100 empty threads (just thread::create and nothing more), top
>> reports 12.6g of virtual memory used.
>>
>> That works out to about 12mb per empty thread.
>
> This seems like a lot, so I tested it with an interactive tclsh. After
> loading the thread package top shows 5560k. Each thread::create adds
> about 1000k. Do you have some other packages loaded in your program?
>
> Joerg

Just a blank interactive tclsh (64 bit).

$ rlwrap tclsh
% package require Thread
2.8.7
% for {set i 0} {$i < 1000} {incr i} {thread::create}
%

And top reports, for the tclsh:

PID NI VIRT RES SWAP S %CPU %MEM TIME+ COMMAND
30010 0 11.8g 273760 0 S 0.0 1.1 0:02.84 tclsh

Only 273760 resident, but tclsh has allocaated 11.8g.

Just a blank tclsh (launched within rlwrap) shows as:

31029 0 6864 4636 0 R 0.0 0.0 0:13.47 tclsh

269k resident per thread -- but the virtual space itself balloons much
more.

Rich <rich@example.invalid> writes:

> Joerg Mertens <joerg-mertens@t-online.de> wrote:
>> Rich <rich@example.invalid> writes:
>>
>>> Linux, 1100 empty threads (just thread::create and nothing more), top
>>> reports 12.6g of virtual memory used.
>>>
>>> That works out to about 12mb per empty thread.
>>
>> This seems like a lot, so I tested it with an interactive tclsh. After
>> loading the thread package top shows 5560k. Each thread::create adds
>> about 1000k. Do you have some other packages loaded in your program?
>>
>> Joerg

I didn't take into account that I did the test on OpenBSD. I also
wouldn't have thought the difference in memory management is so big.

> Just a blank interactive tclsh (64 bit).
>
> $ rlwrap tclsh
> % package require Thread
> 2.8.7
> % for {set i 0} {$i < 1000} {incr i} {thread::create}
> %

Same here, except the Thread package version is 2.8.8

> And top reports, for the tclsh:
>
> PID NI VIRT RES SWAP S %CPU %MEM TIME+ COMMAND
> 30010 0 11.8g 273760 0 S 0.0 1.1 0:02.84 tclsh
>
> Only 273760 resident, but tclsh has allocaated 11.8g.

My top output:

PID PRI NICE SIZE RES STATE WAIT TIME CPU COMMAND
98511 3 0 966M 475M idle ttyin 0:05 0.00% tclsh8.6

SIZE is the total size of the process here. Should be similar to
linux's VIRT column.

> Just a blank tclsh (launched within rlwrap) shows as:
>
> 31029 0 6864 4636 0 R 0.0 0.0 0:13.47 tclsh
>
> 269k resident per thread -- but the virtual space itself balloons much
> more.

Yes, that's the main difference.

Joerg