Re: [dpdk-dev] [PATCH v3 2/4] mempool: add non-IO flag

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 10/12/21 3:04 AM, Dmitry Kozlyuk wrote:
> Mempool is a generic allocator that is not necessarily used for device
> IO operations and its memory for DMA. Add MEMPOOL_F_NON_IO flag to mark
> such mempools.
> Discussion: https://mails.dpdk.org/archives/dev/2021-August/216654.html
> 
> Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
> Acked-by: Matan Azrad <matan@nvidia.com>
> ---
>  doc/guides/rel_notes/release_21_11.rst | 3 +++
>  lib/mempool/rte_mempool.h              | 4 ++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/release_21_11.rst b/doc/guides/rel_notes/release_21_11.rst
> index 5036641842..dbabdc9759 100644
> --- a/doc/guides/rel_notes/release_21_11.rst
> +++ b/doc/guides/rel_notes/release_21_11.rst
> @@ -208,6 +208,9 @@ API Changes
>    the crypto/security operation. This field will be used to communicate
>    events such as soft expiry with IPsec in lookaside mode.
>  
> +* mempool: Added ``MEMPOOL_F_NON_IO`` flag to give a hint to DPDK components
> +  that objects from this pool will not be used for device IO (e.g. DMA).
> +
>  
>  ABI Changes
>  -----------
> diff --git a/lib/mempool/rte_mempool.h b/lib/mempool/rte_mempool.h
> index e2bf40aa09..b48d9f89c2 100644
> --- a/lib/mempool/rte_mempool.h
> +++ b/lib/mempool/rte_mempool.h
> @@ -262,6 +262,7 @@ struct rte_mempool {
>  #define MEMPOOL_F_SC_GET         0x0008 /**< Default get is "single-consumer".*/
>  #define MEMPOOL_F_POOL_CREATED   0x0010 /**< Internal: pool is created. */
>  #define MEMPOOL_F_NO_IOVA_CONTIG 0x0020 /**< Don't need IOVA contiguous objs. */
> +#define MEMPOOL_F_NON_IO         0x0040 /**< Not used for device IO (DMA). */

Doesn't it imply MEMPOOL_F_NO_IOVA_CONTIG?
Shouldn't it reject mempool population with not RTE_BAD_IOVA
iova parameter?

I see that it is just a hint, but just trying to make
full picture consistent.

As the second thought: isn't iova==RTE_BAD_IOVA
sufficient as a hint?

>  
>  /**
>   * @internal When debug is enabled, store some statistics.
> @@ -991,6 +992,9 @@ typedef void (rte_mempool_ctor_t)(struct rte_mempool *, void *);
>   *     "single-consumer". Otherwise, it is "multi-consumers".
>   *   - MEMPOOL_F_NO_IOVA_CONTIG: If set, allocated objects won't
>   *     necessarily be contiguous in IO memory.
> + *   - MEMPOOL_F_NON_IO: If set, the mempool is considered to be
> + *     never used for device IO, i.e. for DMA operations.
> + *     It's a hint to other components and does not affect the mempool behavior.
>   * @return
>   *   The pointer to the new allocated mempool, on success. NULL on error
>   *   with rte_errno set appropriately. Possible rte_errno values include:
>