[Vortex] Thread pool in vortex

[Francis Brosnan Blazquez]

> Hi

Hi Subrahmanya,

> I wanted to understand thread pool mechanism in vortex.

Ok,

> I see that vortex creates a pool of threads for each context and the
> default pool size is 5. This pool is shared across all connections
> created using this context. Is that correct? 

Yes,

> Does it expand/shrink automatically? 

By default no, but you can use vortex_thread_pool_setup to do so (even
at runtime).

> Ideally I would not like to create 5 threads when context is created
> instead it has to be created only when a new thread is required.

You can't anticipate this (for example, a thread from the pool is
required to process channel start reply). You need at least 1 thread in
the pool.

See documentation on [1] for more details:

[1] http://www.aspl.es/fact/files/af-arch/vortex-1.1/html/group__vortex__thread__pool.html

> If the thread pool does not expand automatically then creating many
> connections over the same context wouldn't be a good idea since that
> can lead to performance issues. I see that pool size can be configured
> through environment variable which means the value is applicable to
> any context created in that process. If the pool is not
> expandable/shrinkable then it may not be a good idea to allocate 5
> threads per context. This could be a burden in some scenarios when
> multiple contexts are created in the process. Activities over
> different connections created with different contexts might not be
> uniform. This means creating 5 threads (or whatever value is
> configured through the environment variable) for some of the contexts
> may be optimum and for some this value would be high and for some it
> could be low as well. So not having a expandable/shrinkable pool would
> mean high resource usage even in case of very less activity.

Ok, this is not the case: vortex includes facilities for automatic
thread pool expansion/reduction. At the same time you can also do it
yourself on top of vortex thread pool using
vortex_thread_pool_add/vortex_thread_pool_remove (even at runtime).

> For me the solution seems to be to maintain a global thread pool
> rather than having a thread pool per context and the global thread
> pool has to be shared by different contexts. And, the thread pool has
> to be expanded when there is high activity and there are no threads
> available and reduced when there is less activity. Yes there should be
> a limit on the max number of threads to be created in this pool. This
> way resource usage can be controlled when there is no activity on the
> connections.

Ok, why do you want to create several separated VortexCtx objects but
sharing a global thread pool? I mean, why don't use a single VortexCtx?

> Thanks
> Subrahmanya
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> Vortex at lists.aspl.es
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-- 
Francis Brosnan Blázquez <francis.brosnan at aspl.es>
ASPL
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