RE: [PATCH v2 2/2] ethdev: remove callback checks from fast path

[Sunil Kumar Kori <skori@marvell.com>]

> > From: Sunil Kumar Kori <skori@marvell.com>
> > Sent: Monday, 12 May 2025 17.07
> >
> > rte_eth_fp_ops contains ops for fast path APIs. Each API validates
> > availability of callback and then invoke it.
> > These checks impact data path performace.
> 
> Picking up the discussion from another thread [1]:
> 
> > From: Konstantin Ananyev [mailto:konstantin.ananyev@huawei.com]
> > Sent: Wednesday, 28 May 2025 11.14
> >
> > So what we are saving with that patch: one cmp and one un-taken branch:
> > @@ -6399,8 +6399,6 @@ rte_eth_rx_queue_count(uint16_t port_id,
> > uint16_t
> > queue_id)
> >  		return -EINVAL;
> >  #endif
> >
> > -	if (p->rx_queue_count == NULL)
> > -		return -ENOTSUP;
> >  	return p->rx_queue_count(qd);
> >  }
> 
> These are inline functions, so we also save some code space, instruction cache,
> and possibly an entry in the branch predictor - everywhere these functions are
> instantiated by the compiler.
> 
> >
> > I wonder is how realistic (and measurable) is the gain?
> 
> The performance optimization is mainly targeting the mbuf recycle operations,
> i.e. the hot fast path, where every cycle counts.
> And while optimizing those, the other ethdev fast path callbacks are also
> optimized.
> 
> Yes, although we all agree that there is no downside to this optimization, it
> would be nice to see some performance numbers.
> 
Sure, I will get performance numbers for Marvell platform and will share.

> [1]: https://urldefense.proofpoint.com/v2/url?u=https-
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> HMyaF1_d9IIuq6vHQO6NrIPjaE&m=kCcHSf697ZGAlmjtOXGJe9h7VNzQg7yxhU2aYRbf
> -
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