Re: [dpdk-dev] [PATCH v2 4/4] eal: select IOVA mode as VA for default case

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 16-Jul-19 2:46 PM, jerinj@marvell.com wrote:
> From: Jerin Jacob <jerinj@marvell.com>
> 
> When bus layer selected the preferred mode as RTE_IOVA_DC then
> select the IOVA mode as RTE_IOVA_VA.
> 
> The RTE_IOVA_VA selected as the default because,
> 
> 1) All drivers work in RTE_IOVA_VA mode, irrespective of physical
> address availability.
> 
> 2) By default, the mempool, first asks for IOVA-contiguous memory
> using RTE_MEMZONE_IOVA_CONTIG and this is slow in IOVA as PA mode
> and it may affect the application boot time.
> 
> Signed-off-by: Jerin Jacob <jerinj@marvell.com>
> ---

I should celebrate now :D

>   doc/guides/prog_guide/env_abstraction_layer.rst | 10 ++++++++--
>   lib/librte_eal/linux/eal/eal.c                  |  6 ++----
>   2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> index 77307e3a6..1b0343eee 100644
> --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> @@ -445,8 +445,14 @@ kernels.
>   - if the preferred mode is RTE_IOVA_PA but there is no access to Physical
>     Addresses, then EAL init will fail early, since later probing of the devices
>     would fail anyway,
> -- if the preferred mode is RTE_IOVA_DC then based on the Physical Addresses
> -  availability, the preferred mode is adjusted to RTE_IOVA_PA or RTE_IOVA_VA.
> +- if the preferred mode is RTE_IOVA_DC then select the IOVA mode as RTE_IOVA_VA.
> +  The RTE_IOVA_VA selected as the default because,
> +
> +#. All drivers work in RTE_IOVA_VA mode, irrespective of physical address availability.

Is there anywhere we can document that any new driver must support both 
before being accepted?

> +
> +#. By default, the mempool, first asks for IOVA-contiguous memory using ``RTE_MEMZONE_IOVA_CONTIG``,
> +   and this is slow in IOVA as PA mode and it may affect the application boot time.

I would also add a point about usability improvement for use-cases which 
require large amounts of IOVA-contiguous memory.

Otherwise,

Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

-- 
Thanks,
Anatoly