Re: [dpdk-dev] [PATCH] parray: introduce internal API for dynamic arrays

[Jerin Jacob <jerinjacobk@gmail.com>]

On Tue, Jun 15, 2021 at 12:18 PM Thomas Monjalon <thomas@monjalon.net> wrote:
>
> 14/06/2021 17:48, Morten Brørup:
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > It would be much simpler to just increase RTE_MAX_ETHPORTS to something big enough to hold a sufficiently large array. And possibly add an rte_max_ethports variable to indicate the number of populated entries in the array, for use when iterating over the array.
> >
> > Can we come up with another example than RTE_MAX_ETHPORTS where this library provides a better benefit?
>
> What is big enough?
> Is 640KB enough for RAM? ;)

If I understand it correctly, Linux process allocates 640KB due to
that fact currently
struct rte_eth_dev rte_eth_devices[RTE_MAX_ETHPORTS] is global and it
is from BSS.

If we make this from heap i.e use malloc() to allocate this memory
then in my understanding Linux
really won't allocate the real page for backend memory until unless,
someone write/read to this memory.

i.e it will be free virtual memory using Linux memory management help.
If so, we can keep large values for RTE_MAX_ETHPORTS
without wasting any "real" memory even though the system has a few ports.

Thoughts?



>
> When dealing with microservices switching, the numbers can increase very fast.
>
>