[argobots-discuss] externally allocated stacks and unnamed (detached) threads

[Shintaro Iwasaki]

Hi Phil,

Thanks for your question!

Calling a custom stack destructor for an unnamed ULT is possible within the
current Argobots infrastructure. This is related to this issue:
https://github.com/pmodels/argobots/issues/16.

For the detailed implementation, please find the complete code here
(collapsed):
https://github.com/pmodels/argobots/issues/274#issuecomment-785221242.
Though you have to call init_stack_key() and finalize_stack_key() to use
this, it should be simple enough: you just basically change
allocate_stack() and free_stack() for your workload.

I believe this is the quick path to implement your idea. But maybe a more
intuitive stack-free-hook interface would be preferable (this request is
not the first time). Please let me know if you need such a new interface
(especially if your idea works well).

Thanks,
Shintaro

On Wed, Nov 17, 2021 at 2:15 PM Phil Carns via discuss <
discuss at lists.argobots.org> wrote:

> Hi all,
>
> We've been thinking about some memory optimizations for which it might
> be easier if our own code provided the stack memory for newly created
> ULTs so that we have full control over the allocation strategy.  This
> seems pretty straightforward with the ABT_thread_attr_set_stack() function:
>
>
> https://www.argobots.org/doxygen/latest/d2/df6/group__ULT__ATTR.html#gac8f39be20d677898c45293c5ce31eea0
>
> However, our use case often creates unnamed (detached) threads by
> setting the ABT_thread_create() newthread argument to NULL.  I can
> elaborate if needed, but the short story is that this is a really
> natural fit for RPC handlers in our model:
>
>
> https://www.argobots.org/doxygen/latest/d0/d6d/group__ULT.html#ga73bd1f04ce57def336cb20cdec9b14bd
>
> Is it possible to do both (provide an externally managed stack pointer,
> and use unnamed ULTs)?  From the documentation it looks like the answer
> is probably no, because the caller who created the stack allocation
> doesn't explicitly free the ULT, and thus doesn't have a way to free the
> stack after the ULT is complete.
>
> I wanted to double check though before I start thinking about
> alternatives, though.
>
> thanks!
>
> -Phil
>
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>
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