Re: [dpdk-dev] [PATCH] build: add meson option of "max_memseg_lists" and "mbuf_refcnt_atomic"

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Sep 02, 2021 at 10:48:05PM +0800, Kefu Chai wrote:
> RTE_MAX_MEMSEG_LISTS = 128 is not enough for some use cases, so add an
> option so user can override it.

How big a value do you need? Can you share anything about the use-case
where you are hitting this limit?

> RTE_MBUF_REFCNT_ATOMIC = 0 is enough for applications like Seastar,
> where it's safe to assume that the mbuf refcnt is only updated by a single
> core only.
> 
> Signed-off-by: Kefu Chai <tchaikov@gmail.com>
> ---
>  config/meson.build  | 5 ++++-
>  config/rte_config.h | 2 --
>  meson_options.txt   | 5 +++++
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/config/meson.build b/config/meson.build
> index 3b5966ec2f..72dd461198 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -301,7 +301,10 @@ if dpdk_conf.get('RTE_ARCH_64')
>  else # for 32-bit we need smaller reserved memory areas
>      dpdk_conf.set('RTE_MAX_MEM_MB', 2048)
>  endif
> -
> +dpdk_conf.set('RTE_MAX_MEMSEG_LISTS', get_option('max_memseg_lists'))
> +if get_option('mbuf_refcnt_atomic')
> +  dpdk_conf.set('RTE_MBUF_REFCNT_ATOMIC', true)
> +endif
>  
>  compile_time_cpuflags = []
>  subdir(arch_subdir)
> diff --git a/config/rte_config.h b/config/rte_config.h
> index 590903c07d..0a659f5e1a 100644
> --- a/config/rte_config.h
> +++ b/config/rte_config.h
> @@ -29,7 +29,6 @@
>  
>  /* EAL defines */
>  #define RTE_MAX_HEAPS 32
> -#define RTE_MAX_MEMSEG_LISTS 128
>  #define RTE_MAX_MEMSEG_PER_LIST 8192
>  #define RTE_MAX_MEM_MB_PER_LIST 32768
>  #define RTE_MAX_MEMSEG_PER_TYPE 32768
> @@ -50,7 +49,6 @@
>  
>  /* mbuf defines */
>  #define RTE_MBUF_DEFAULT_MEMPOOL_OPS "ring_mp_mc"
> -#define RTE_MBUF_REFCNT_ATOMIC 1
>  #define RTE_PKTMBUF_HEADROOM 128
>  
>  /* ether defines */
> diff --git a/meson_options.txt b/meson_options.txt
> index 0e92734c49..c0e8958797 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -38,6 +38,11 @@ option('max_lcores', type: 'integer', value: 128, description:
>         'maximum number of cores/threads supported by EAL')
>  option('max_numa_nodes', type: 'integer', value: 32, description:
>         'maximum number of NUMA nodes supported by EAL')
> +option('max_memseg_lists', type: 'integer', value: 128, description:
> +       'maximum number of dynamic arrays holding memsegs')
> +option('mbuf_refcnt_atomic', type: 'boolean', value: true, description:
> +       'atomically access the mbuf refcnt')
> +

No blank line after the option. I'd suggest renaming it to
"atomic_mbuf_ref_counts" to make the entry name more readable - at the cost
of it being longer, unfortunately.

/Bruce