Re: [dpdk-dev] [PATCH] rte_delay_us can be replaced with user function

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Hi,

2016-07-19 14:42, jozmarti@cisco.com:
> when running single-core, some drivers tend to call rte_delay_us for a
> long time, and that is causing packet drops.
> Attached patch introduces 2 new functions:
> 
> void rte_delay_us_callback_register(void(*userfunc)(unsigned));
> void rte_delay_us_callback_unregister(void);
> 
> First one replaces rte_delay_us with userfunc and second one restores
> original rte_delay_us.

I think we could avoid the function unregister by exporting the
default implementation (let's say rte_delay_us_block).


> +REGISTER_TEST_COMMAND(user_delay_us, test_user_delay_us);

Thanks for providing an unit test.


> --- a/lib/librte_eal/common/eal_common_timer.c
> +++ b/lib/librte_eal/common/eal_common_timer.c
>  void
>  rte_delay_us(unsigned us)
>  {
> +	if (unlikely(rte_delay_us_override != NULL))
> +	{
> +	    rte_delay_us_override(us);
> +	    return;
> +	}

Why not always call the registered callback and initialize it
to the default implementation (maybe using a constructor)?