Re: [dpdk-dev] [PATCH 0/5] lib/ring: templates to support custom element size

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Honnappa Nagarahalli
> Sent: Wednesday, August 28, 2019 8:16 PM
> To: olivier.matz@6wind.com; yipeng1.wang@intel.com;
> sameh.gobriel@intel.com; bruce.richardson@intel.com;
> pablo.de.lara.guarch@intel.com; honnappa.nagarahalli@arm.com
> Cc: dev@dpdk.org; dharmik.thakkar@arm.com; gavin.hu@arm.com;
> ruifeng.wang@arm.com; nd@arm.com
> Subject: [dpdk-dev] [PATCH 0/5] lib/ring: templates to support custom element
> size
> 
> The current rte_ring hard-codes the type of the ring element to 'void *', hence
> the size of the element is hard-coded to 32b/64b. Since the ring element type is
> not an input to rte_ring APIs, it results in couple of issues:
> 
> 1) If an application requires to store an element which is not 64b, it
>    needs to writes its own ring APIs similar to rte_event_ring APIs. This
>    creates additional burden on the programmers, who simply end up making
>    work-arounds and often waste memory.

If we are taking this path, Could you change rte_event_ring implementation based
on new framework?



> 2) If there are multiple libraries that store elements of the same
>    type, currently they would have to write their own rte_ring APIs. This
>    results in code duplication.
> 
> This patch consists of 4 parts:
> 1) New APIs to support configurable ring element size
>    These will help reduce code duplication in the templates. I think these
>    can be made internal (do not expose to DPDK applications, but expose to
>    DPDK libraries), feedback needed.
> 
> 2) rte_ring templates
>    The templates provide an easy way to add new APIs for different ring
>    element types/sizes which can be used by multiple libraries. These
>    also allow for creating APIs to store elements of custom types
>    (for ex: a structure)
> 
>    The template needs 4 parameters:
>    a) RTE_RING_TMPLT_API_SUFFIX - This is used as a suffix to the
>       rte_ring APIs.
>       For ex: if RTE_RING_TMPLT_API_SUFFIX is '32b', the API name will be
>       rte_ring_create_32b
>    b) RTE_RING_TMPLT_ELEM_SIZE - Size of the ring element in bytes.
>       For ex: sizeof(uint32_t)
>    c) RTE_RING_TMPLT_ELEM_TYPE - Type of the ring element.
>       For ex: uint32_t. If a common ring library does not use a standard
>       data type, it should create its own type by defining a structure
>       with standard data type. For ex: for an elment size of 96b, one
>       could define a structure
> 
>       struct s_96b {
>           uint32_t a[3];
>       }
>       The common library can use this structure to define
>       RTE_RING_TMPLT_ELEM_TYPE.
> 
>       The application using this common ring library should define its
>       element type as a union with the above structure.
> 
>       union app_element_type {
>           struct s_96b v;
>           struct app_element {
>               uint16_t a;
>               uint16_t b;
>               uint32_t c;
>               uint32_t d;
>           }
>       }
>    d) RTE_RING_TMPLT_EXPERIMENTAL - Indicates if the new APIs being defined
>       are experimental. Should be set to empty to remove the experimental
>       tag.
> 
>    The ring library consists of some APIs that are defined as inline
>    functions and some APIs that are non-inline functions. The non-inline
>    functions are in rte_ring_template.c. However, this file needs to be
>    included in other .c files. Any feedback on how to handle this is
>    appreciated.
> 
>    Note that the templates help create the APIs that are dependent on the
>    element size (for ex: rte_ring_create, enqueue/dequeue etc). Other APIs
>    that do NOT depend on the element size do not need to be part of the
>    template (for ex: rte_ring_dump, rte_ring_count, rte_ring_free_count
>    etc).
> 
> 3) APIs for 32b ring element size
>    This uses the templates to create APIs to enqueue/dequeue elements of
>    size 32b.
> 
> 4) rte_hash libray is changed to use 32b ring APIs
>    The 32b APIs are used in rte_hash library to store the free slot index
>    and free bucket index.
> 
> This patch results in following checkpatch issue:
> WARNING:UNSPECIFIED_INT: Prefer 'unsigned int' to bare use of 'unsigned'
> 
> The patch is following the rules in the existing code. Please let me know if this
> needs to be fixed.
> 
> Honnappa Nagarahalli (5):
>   lib/ring: apis to support configurable element size
>   lib/ring: add template to support different element sizes
>   tools/checkpatch: relax constraints on __rte_experimental
>   lib/ring: add ring APIs to support 32b ring elements
>   lib/hash: use ring with 32b element size to save memory
> 
>  devtools/checkpatches.sh             |  11 +-
>  lib/librte_hash/rte_cuckoo_hash.c    |  55 ++---
>  lib/librte_hash/rte_cuckoo_hash.h    |   2 +-
>  lib/librte_ring/Makefile             |   9 +-
>  lib/librte_ring/meson.build          |  11 +-
>  lib/librte_ring/rte_ring.c           |  34 ++-
>  lib/librte_ring/rte_ring.h           |  72 ++++++
>  lib/librte_ring/rte_ring_32.c        |  19 ++
>  lib/librte_ring/rte_ring_32.h        |  36 +++
>  lib/librte_ring/rte_ring_template.c  |  46 ++++
> lib/librte_ring/rte_ring_template.h  | 330 +++++++++++++++++++++++++++
>  lib/librte_ring/rte_ring_version.map |   4 +
>  12 files changed, 582 insertions(+), 47 deletions(-)  create mode 100644
> lib/librte_ring/rte_ring_32.c  create mode 100644 lib/librte_ring/rte_ring_32.h
> create mode 100644 lib/librte_ring/rte_ring_template.c
>  create mode 100644 lib/librte_ring/rte_ring_template.h
> 
> --
> 2.17.1