Re: [PATCH v3 1/3] eal: add lcore poll busyness telemetry

[Kevin Laatz <kevin.laatz@intel.com>]

On 29/08/2022 14:44, Morten Brørup wrote:
>> From: Kevin Laatz [mailto:kevin.laatz@intel.com]
>> Sent: Monday, 29 August 2022 15.37
>>
>> On 29/08/2022 13:49, Morten Brørup wrote:
>>> From: Kevin Laatz [mailto:kevin.laatz@intel.com]
>>> Sent: Monday, 29 August 2022 14.37
>>>> The patches currently include runtime options to enable/disable the
>> feature via API and via telemetry endpoints. We have run performance
>> tests and have failed to measure any performance impact with the
>> feature runtime disabled.
>>> Lots of features are added to DPDK all the time, and they all use the
>> same "insignificant performance impact" argument. But the fact is, each
>> added test-and-branch has some small performance impact (and consume
>> some entries in the branch prediction table, which may impact
>> performance elsewhere). If you add a million features using this
>> argument, there will be a significant and measurable performance
>> impact.
>>> Which is why I keep insisting on the ability to omit non-core
>> features from DPDK at build time.
>>
>> I think there's general consensus in having a buildtime option to
>> disable it.
>>
>> Do we agree that it should be buildtime enabled, and runtime disabled
>> by
>> default (so just the single additional branch by default), with the
>> meson option available to disable it completely at buildtime?
> No. This feature is in the fast path, so please follow the "enable_trace_fp" design pattern, which also has fast path trace disabled at build time.
>
Ok, will make this change for the v4. Thanks!