Multiple rte_launch_remote multiple times on main lcore

Multiple rte_launch_remote multiple times on main lcore

[Antonio Di Bacco]

Is it possible to launch multiple threads on the main lcore?
Who will be in charge of scheduling those threads on the main lcore
(main lcore is isolated)?

Not the OS I suppose.

Thank you

Re: Multiple rte_launch_remote multiple times on main lcore

[Stephen Hemminger]

On Tue, 20 Jun 2023 17:33:59 +0200
Antonio Di Bacco <a.dibacco.ks@gmail.com> wrote:

> Is it possible to launch multiple threads on the main lcore?
> Who will be in charge of scheduling those threads on the main lcore
> (main lcore is isolated)?
> 
> Not the OS I suppose.
> 
> Thank you

If you start trying to add threads like this, it will lead to
all sorts of locking problems.  When one thread gets the lock
and then gets preempted by the scheduler and another thread
(bound to same lcore) tries to acquire the lock, it will spin
and wait until the first thread is rescheduled.

DPDK was designed for dedicated threads per lcore.

Re: Multiple rte_launch_remote multiple times on main lcore

[Antonio Di Bacco]

This is very useful. Anyway, just on main_lcore, could I launch many
pthreads (with pthread_create) ?

Does this interfere with DPDK?

On Sun, Jun 25, 2023 at 4:49 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Tue, 20 Jun 2023 17:33:59 +0200
> Antonio Di Bacco <a.dibacco.ks@gmail.com> wrote:
>
> > Is it possible to launch multiple threads on the main lcore?
> > Who will be in charge of scheduling those threads on the main lcore
> > (main lcore is isolated)?
> >
> > Not the OS I suppose.
> >
> > Thank you
>
> If you start trying to add threads like this, it will lead to
> all sorts of locking problems.  When one thread gets the lock
> and then gets preempted by the scheduler and another thread
> (bound to same lcore) tries to acquire the lock, it will spin
> and wait until the first thread is rescheduled.
>
> DPDK was designed for dedicated threads per lcore.

Re: Multiple rte_launch_remote multiple times on main lcore

[Stephen Hemminger]

On Tue, 27 Jun 2023 20:20:28 +0200
Antonio Di Bacco <a.dibacco.ks@gmail.com> wrote:

> This is very useful. Anyway, just on main_lcore, could I launch many
> pthreads (with pthread_create) ?
> 
> Does this interfere with DPDK?

DPDK is not designed for random additional threads.
You could use rte_ctrl_thread_create or do the working of creating, binding threads to cores,
and registering; but the startup does that already.

DPDK is designed for run to completion model where there is one thread bound to a core (and isolated).
You can try other things, but that makes things worse not better.
performance will be worse, can deadlock, will require additional locking etc.