Re: [PATCH v4 2/3] event/dlb2: add support for dynamic HL entries

[Jerin Jacob <jerinjacobk@gmail.com>]

On Thu, May 2, 2024 at 1:16 AM Abdullah Sevincer
<abdullah.sevincer@intel.com> wrote:
>
> In DLB 2.5, hardware assist is available, complementing the Delayed
> token POP software implementation. When it is enabled, the feature
> works as follows:
>
> It stops CQ scheduling when the inflight limit associated with the CQ
> is reached. So the feature is activated only if the core is
> congested. If the core can handle multiple atomic flows, DLB will not
> try to switch them. This is an improvement over SW implementation
> which always switches the flows.
>
> The feature will resume CQ scheduling when the number of pending
> completions fall below a configured threshold.
>
> DLB has 64 LDB ports and 2048 HL entries. If all LDB ports are used,
> possible HL entries per LDB port equals 2048 / 64 = 32. So, the
> maximum CQ depth possible is 16, if all 64 LB ports are needed in a
> high-performance setting.
>
> In case all CQs are configured to have HL = 2* CQ Depth as a
> performance option, then the calculation of HL at the time of domain
> creation will be based on maximum possible dequeue depth. This could
> result in allocating too many HL  entries to the domain as DLB only
> has limited number of HL entries to be allocated. Hence, it is best
> to allow application to specify HL entries as a command line argument
> and override default allocation. A summary of usage is listed below:
>
> When 'use_default_hl = 1', Per port HL is set to
> DLB2_FIXED_CQ_HL_SIZE (32) and command line parameter
> alloc_hl_entries is ignored.
>
> When 'use_default_hl = 0', Per LDB port HL = 2 * CQ depth and per
> port HL is set to 2 * DLB2_FIXED_CQ_HL_SIZE.
>
> User should calculate needed HL entries based on CQ depths the
> application will use and specify it as command line parameter
> 'alloc_hl_entries'. This will be used to allocate HL entries.
> Hence, alloc_hl_entries = (Sum of all LDB ports CQ depths * 2).
>
> If alloc_hl_entries is not specified, then Total HL entries for the
> vdev = num_ldb_ports * 64.
>
> Signed-off-by: Abdullah Sevincer <abdullah.sevincer@intel.com>

>         }
> diff --git a/drivers/event/dlb2/dlb2_priv.h b/drivers/event/dlb2/dlb2_priv.h
> index d6828aa482..dc9f98e142 100644
> --- a/drivers/event/dlb2/dlb2_priv.h
> +++ b/drivers/event/dlb2/dlb2_priv.h
> @@ -52,6 +52,8 @@
>  #define DLB2_PRODUCER_COREMASK "producer_coremask"
>  #define DLB2_DEFAULT_LDB_PORT_ALLOCATION_ARG "default_port_allocation"
>  #define DLB2_ENABLE_CQ_WEIGHT_ARG "enable_cq_weight"
> +#define DLB2_USE_DEFAULT_HL "use_default_hl"
> +#define DLB2_ALLOC_HL_ENTRIES "alloc_hl_entries"


1)Update doc/guides/eventdevs/dlb2.rst for new devargs
2)Please release note PMD section for this feature.