[20.11 PATCH v1 1/2] eal: add lcore busyness telemetry

[Burakov, Anatoly]

On 15-Jul-22 2:12 PM, Anatoly Burakov wrote:
> Currently, there is no way to measure lcore busyness in a passive way,
> without any modifications to the application. This patch adds a new EAL
> API that will be able to passively track core busyness.
> 
> The busyness is calculated by relying on the fact that most DPDK API's
> will poll for packets. Empty polls can be counted as "idle", while
> non-empty polls can be counted as busy. To measure lcore busyness, we
> simply call the telemetry timestamping function with the number of polls
> a particular code section has processed, and count the number of cycles
> we've spent processing empty bursts. The more empty bursts we encounter,
> the less cycles we spend in "busy" state, and the less core busyness
> will be reported.
> 
> In order for all of the above to work without modifications to the
> application, the library code needs to be instrumented with calls to
> the lcore telemetry busyness timestamping function. The following parts
> of DPDK are instrumented with lcore telemetry calls:
> 
> - All major driver API's:
>    - ethdev
>    - cryptodev
>    - compressdev
>    - regexdev
>    - bbdev
>    - rawdev
>    - eventdev
> - Some additional libraries:
>    - ring
>    - distributor
> 
> To avoid performance impact from having lcore telemetry support, a
> global variable is exported by EAL, and a call to timestamping function
> is wrapped into a macro, so that whenever telemetry is disabled, it only
> takes one additional branch and no function calls are performed. It is
> also possible to disable it at compile time by commenting out
> RTE_LCORE_BUSYNESS from build config.
> 
> This patch also adds a telemetry endpoint to report lcore busyness, as
> well as telemetry endpoints to enable/disable lcore telemetry.
> 
> Signed-off-by: Kevin Laatz <kevin.laatz at intel.com>
> Signed-off-by: Conor Walsh <conor.walsh at intel.com>
> Signed-off-by: David Hunt <david.hunt at intel.com>
> Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
> ---

These patches are to be applied on top of 20.11, so please ignore this 
patchset. I've already marked it as "Not Applicable" in patchwork.

-- 
Thanks,
Anatoly