Re: [dpdk-dev] [PATCH 13/41] eal: replace memseg with memseg lists

[Olivier Matz <olivier.matz@6wind.com>]

On Sat, Mar 03, 2018 at 01:46:01PM +0000, Anatoly Burakov wrote:

[...]

> --- a/config/common_base
> +++ b/config/common_base
> @@ -61,7 +61,20 @@ CONFIG_RTE_CACHE_LINE_SIZE=64
>  CONFIG_RTE_LIBRTE_EAL=y
>  CONFIG_RTE_MAX_LCORE=128
>  CONFIG_RTE_MAX_NUMA_NODES=8
> -CONFIG_RTE_MAX_MEMSEG=256
> +CONFIG_RTE_MAX_MEMSEG_LISTS=32
> +# each memseg list will be limited to either RTE_MAX_MEMSEG_PER_LIST pages
> +# or RTE_MAX_MEM_PER_LIST gigabytes worth of memory, whichever is the smallest
> +CONFIG_RTE_MAX_MEMSEG_PER_LIST=8192
> +CONFIG_RTE_MAX_MEM_PER_LIST=32
> +# a "type" is a combination of page size and NUMA node. total number of memseg
> +# lists per type will be limited to either RTE_MAX_MEMSEG_PER_TYPE pages (split
> +# over multiple lists of RTE_MAX_MEMSEG_PER_LIST pages), or RTE_MAX_MEM_PER_TYPE
> +# gigabytes of memory (split over multiple lists of RTE_MAX_MEM_PER_LIST),
> +# whichever is the smallest
> +CONFIG_RTE_MAX_MEMSEG_PER_TYPE=32768
> +CONFIG_RTE_MAX_MEM_PER_TYPE=128
> +# legacy mem mode only
> +CONFIG_RTE_MAX_LEGACY_MEMSEG=256

Would it be possible to suffix CONFIG_RTE_MAX_MEM_PER_LIST and
CONFIG_RTE_MAX_MEM_PER_TYPE with _GB? It's not that obvious that is it
gigabytes.

What is the impact of changing one of these values on the ABI? And what
would be the impact on performance? The underlying question is: shall we
increase these values to avoid changing them later?