[dpdk-dev] [PATCH v1] examples/l3fwd-power: add telemetry mode support
Burakov, Anatoly
anatoly.burakov at intel.com
Wed May 22 11:46:15 CEST 2019
On 21-May-19 3:53 PM, Pattan, Reshma wrote:
>
>
>> -----Original Message-----
>> From: Burakov, Anatoly
>> Sent: Monday, May 20, 2019 2:17 PM
>> To: Pattan, Reshma <reshma.pattan at intel.com>; dev at dpdk.org
>> Cc: Hunt, David <david.hunt at intel.com>; Ma, Liang J <liang.j.ma at intel.com>
>> Subject: Re: [PATCH v1] examples/l3fwd-power: add telemetry mode support
>>
>
> <snip>
>
>>> ---
>>
>> <snip>
>>
>>> + poll_count = 0;
>>> + prev_tel_tsc = cur_tsc;
>>> + /* update stats for telemetry */
>>> + rte_spinlock_lock(&stats[lcore_id].telemetry_lock);
>>> + stats[lcore_id].ep_nep[0] = ep_nep[0];
>>> + stats[lcore_id].ep_nep[1] = ep_nep[1];
>>> + stats[lcore_id].fp_nfp[0] = fp_nfp[0];
>>> + stats[lcore_id].fp_nfp[1] = fp_nfp[1];
>>> + stats[lcore_id].br = br;
>>> + rte_spinlock_unlock(&stats[lcore_id].telemetry_lock);
>>
>> Locking here seems relatively rare (per-lcore and once every N polls), but any
>> locking on a hotpath makes me nervous. What is the current performance
>> impact of this? Should we bother improving?
>
> The performance impact is negligible, in thousands.
In thousands of packets? Out of?
>
>>>
>>> if (!strncmp(lgopts[option_index].name,
>>> @@ -1869,6 +2068,52 @@ init_power_library(void)
>>> return ret;
>>> }
>>> static void
>>> +update_telemetry(__attribute__((unused)) struct rte_timer *tim,
>>> + __attribute__((unused)) void *arg)
>>> +{
>>
>> I would question the need to put telemetry on a high precision 10ms timer. Is
>> there any reason why we cannot gather telemetry, say, once every 100ms, and
>> why we cannot do so from interrupt thread using alarm API? Using high-
>> precision timer API here seems like an overkill.
>
> The l3-power uses the timers , so followed the same. But I am ok
> to use ALARM api.
Maybe just change the timer period then? 10ms to update telemetry looks
way too often to me. Do we really expect telemetry to be gathered every
10ms?
>
> Thanks,
> Reshma
>
--
Thanks,
Anatoly
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