> 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?
>
> 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;
> +
> 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.
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);
> +}
