Re: [PATCH v2 1/1] mempool: implement index-based per core cache

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, Jan 13, 2022 at 11:06 AM Dharmik Thakkar
<dharmik.thakkar@arm.com> wrote:
>
> Current mempool per core cache implementation stores pointers to mbufs
> On 64b architectures, each pointer consumes 8B
> This patch replaces it with index-based implementation,
> where in each buffer is addressed by (pool base address + index)
> It reduces the amount of memory/cache required for per core cache
>
> L3Fwd performance testing reveals minor improvements in the cache
> performance (L1 and L2 misses reduced by 0.60%)
> with no change in throughput
>
> Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---

>
>         /* Now fill in the response ... */
> +#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE

Instead of having this #ifdef clutter everywhere for the pair,
I think, we can define RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE once,
and have a different implementation.
i.e
#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE
void x()
{

}
void y()
{

}
#else

void x()
{

}
void y()
{

}

#endif

call
x();
y();

in the main code.

> diff --git a/lib/mempool/rte_mempool_ops_default.c b/lib/mempool/rte_mempool_ops_default.c
> index 22fccf9d7619..3543cad9d4ce 100644
> --- a/lib/mempool/rte_mempool_ops_default.c
> +++ b/lib/mempool/rte_mempool_ops_default.c
> @@ -127,6 +127,13 @@ rte_mempool_op_populate_helper(struct rte_mempool *mp, unsigned int flags,
>                 obj = va + off;
>                 obj_cb(mp, obj_cb_arg, obj,
>                        (iova == RTE_BAD_IOVA) ? RTE_BAD_IOVA : (iova + off));
> +#ifdef RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE

This is the only place used in C code.
Since we are going compile time approach. Can make this unconditional?
That will enable the use of this model in the application, without
recompiling DPDK.
All application needs to

#define RTE_MEMPOOL_INDEX_BASED_LCORE_CACHE 1
#include <rte_mempool.h>

I believe enabling such structuring helps to avoid DPDK recompilation of code.


> +               /* Store pool base value to calculate indices for index-based
> +                * lcore cache implementation
> +                */
> +               if (i == 0)
> +                       mp->pool_base_value = obj;
> +#endif
>                 rte_mempool_ops_enqueue_bulk(mp, &obj, 1);
>                 off += mp->elt_size + mp->trailer_size;
>         }
> --
> 2.17.1
>