Hi Morten,
On 2023/10/23 16:58, Morten Brørup wrote:
>> From: Chengwen Feng [mailto:fengcheng...@huawei.com]
>> Sent: Monday, 23 October 2023 06.08
>>
>> Current, the lcore usage only display two key fields: busy_cycles and
>> total_cycles, which is inconvenient to obtain the usage ratio
>> immediately. So adds lcore usage ratio field.
>
> Usage ratio in percentage is only useful if it doesn't vary much over time.
> Which use cases don't have a varying traffic pattern with busy hours and
> off-peak hours?
Yes, it indeed.
There have too way:
1\ only compare increment of busy&total, which this ratio have less reference.
2\ clean the busy&total before do an metrics, then this ratio become usefull
>
>>
>> Signed-off-by: Chengwen Feng <fengcheng...@huawei.com>
>> ---
>
> [...]
>
>> +static float
>> +calc_usage_ratio(const struct rte_lcore_usage *usage)
>> +{
>> + return (usage->busy_cycles * 100.0) / (usage->total_cycles == 0 ? 1 :
>> usage->total_cycles);
>> +}
>
> This correctly prevents division by zero. If total_cycles by some freak
> accident isn't updated, the result will be a very big number. You might
> consider this alternative:
>
> return usage->total_cycles != 0 ? (usage->busy_cycles * 100.0) /
> usage->total_cycles : (float)0;
ok
>
>> +
>> static int
>> lcore_dump_cb(unsigned int lcore_id, void *arg)
>> {
>> @@ -462,8 +468,9 @@ lcore_dump_cb(unsigned int lcore_id, void *arg)
>> /* Guard against concurrent modification of lcore_usage_cb. */
>> usage_cb = lcore_usage_cb;
>> if (usage_cb != NULL && usage_cb(lcore_id, &usage) == 0) {
>> - if (asprintf(&usage_str, ", busy cycles %"PRIu64"/%"PRIu64,
>> - usage.busy_cycles, usage.total_cycles) < 0) {
>> + if (asprintf(&usage_str, ", busy cycles %"PRIu64"/%"PRIu64"
>> (ratio %.3f%%)",
>
> Is "%.3f%%" the community preference for human readable CPU usage percentages?
>
> I prefer "%.02f%%", but don't object to the suggested format.
maybe %.02f is more common, will change in v2
>
> NB: The format also applies to format_usage_ratio() below.
>
>> + usage.busy_cycles, usage.total_cycles,
>> + calc_usage_ratio(&usage)) < 0) {
>> return -ENOMEM;
>> }
>> }
>> @@ -511,11 +518,19 @@ struct lcore_telemetry_info {
>> struct rte_tel_data *d;
>> };
>>
>> +static void
>> +format_usage_ratio(char *buf, uint16_t size, const struct rte_lcore_usage
>> *usage)
>> +{
>> + float ratio = calc_usage_ratio(usage);
>> + snprintf(buf, size, "%.3f%%", ratio);
>> +}
>
> .
>
