[PATCH v5 1/4] eal: add lcore info in telemetry

[Kevin Laatz]

On 16/12/2022 10:21, Robin Jarry wrote:
> Report the same information than rte_lcore_dump() in the telemetry
> API into /eal/lcore/list and /eal/lcore/info,ID.
>
> Example:
>
>    --> /eal/lcore/info,3
>    {
>      "/eal/lcore/info": {
>        "lcore_id": 3,
>        "socket": 0,
>        "role": "RTE",
>        "cpuset": [
>          3
>        ]
>      }
>    }
>
> Signed-off-by: Robin Jarry <rjarry at redhat.com>
> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> ---
> v4 -> v5: No change
>
>   lib/eal/common/eal_common_lcore.c | 96 +++++++++++++++++++++++++++++++
>   1 file changed, 96 insertions(+)
>
> diff --git a/lib/eal/common/eal_common_lcore.c b/lib/eal/common/eal_common_lcore.c
> index 06c594b0224f..16548977dce8 100644
> --- a/lib/eal/common/eal_common_lcore.c
> +++ b/lib/eal/common/eal_common_lcore.c
> @@ -10,6 +10,9 @@
>   #include <rte_errno.h>
>   #include <rte_lcore.h>
>   #include <rte_log.h>
> +#ifndef RTE_EXEC_ENV_WINDOWS
> +#include <rte_telemetry.h>
> +#endif
>   
>   #include "eal_private.h"
>   #include "eal_thread.h"
> @@ -456,3 +459,96 @@ rte_lcore_dump(FILE *f)
>   {
>   	rte_lcore_iterate(lcore_dump_cb, f);
>   }
> +
> +#ifndef RTE_EXEC_ENV_WINDOWS
> +static int
> +lcore_telemetry_id_cb(unsigned int lcore_id, void *arg)
> +{
> +	struct rte_tel_data *d = arg;
> +	return rte_tel_data_add_array_int(d, lcore_id);
> +}
> +
> +static int
> +handle_lcore_list(const char *cmd __rte_unused,
> +			const char *params __rte_unused,
> +			struct rte_tel_data *d)
> +{
> +	int ret = rte_tel_data_start_array(d, RTE_TEL_INT_VAL);
> +	if (ret)
> +		return ret;
> +	return rte_lcore_iterate(lcore_telemetry_id_cb, d);
> +}
> +
> +struct lcore_telemetry_info {
> +	unsigned int lcore_id;
> +	struct rte_tel_data *d;
> +};
> +
> +static int
> +lcore_telemetry_info_cb(unsigned int lcore_id, void *arg)
> +{
> +	struct lcore_telemetry_info *info = arg;
> +	struct rte_config *cfg = rte_eal_get_configuration();
> +	struct rte_tel_data *cpuset;
> +	const char *role;
> +	unsigned int cpu;
> +
> +	if (info->lcore_id != lcore_id)
> +		return 0;
> +
> +	switch (cfg->lcore_role[lcore_id]) {
> +	case ROLE_RTE:
> +		role = "RTE";
> +		break;
> +	case ROLE_SERVICE:
> +		role = "SERVICE";
> +		break;
> +	case ROLE_NON_EAL:
> +		role = "NON_EAL";
> +		break;
> +	default:
> +		role = "UNKNOWN";
> +		break;
> +	}
> +	rte_tel_data_start_dict(info->d);
> +	rte_tel_data_add_dict_int(info->d, "lcore_id", lcore_id);
> +	rte_tel_data_add_dict_int(info->d, "socket", rte_lcore_to_socket_id(lcore_id));
> +	rte_tel_data_add_dict_string(info->d, "role", role);
> +	cpuset = rte_tel_data_alloc();
> +	if (!cpuset)
> +		return -ENOMEM;
> +	rte_tel_data_start_array(cpuset, RTE_TEL_INT_VAL);
> +	for (cpu = 0; cpu < CPU_SETSIZE; cpu++)
> +		if (CPU_ISSET(cpu, &lcore_config[lcore_id].cpuset))
> +			rte_tel_data_add_array_int(cpuset, cpu);
> +	rte_tel_data_add_dict_container(info->d, "cpuset", cpuset, 0);
> +
> +	return 0;
> +}
> +
> +static int
> +handle_lcore_info(const char *cmd __rte_unused, const char *params, struct rte_tel_data *d)
> +{
> +	struct lcore_telemetry_info info = { .d = d };
> +	char *endptr = NULL;
> +	if (params == NULL || strlen(params) == 0)
> +		return -EINVAL;
> +	errno = 0;
> +	info.lcore_id = strtoul(params, &endptr, 10);
> +	if (errno)
> +		return -errno;
> +	if (endptr == params)
> +		return -EINVAL;
> +	return rte_lcore_iterate(lcore_telemetry_info_cb, &info);
> +}
> +
> +RTE_INIT(lcore_telemetry)
> +{
> +	rte_telemetry_register_cmd(
> +			"/eal/lcore/list", handle_lcore_list,
> +			"List of lcore ids. Takes no parameters");
> +	rte_telemetry_register_cmd(
> +			"/eal/lcore/info", handle_lcore_info,
> +			"Returns lcore info. Parameters: int lcore_id");
> +}
> +#endif /* !RTE_EXEC_ENV_WINDOWS */

Hi Robin,

Thanks for taking the time to work on this. It is a good implementation 
for debug use-cases.

I have 2 suggestions which would improve the usability of the data:
1. Could we make the lcore_id paramater on /eal/lcore/info optional? 
This would allow users to read info for all lcores in the application at 
once.
2. Could we add 2 additional telemetry endpoints? One which returns an 
array of busy_cycles values and the other returns an array of 
total_cycles values. These arrays could be used in conjunction with the 
/eal/lcore/list endpoint to quickly read the usage related metrics. I've 
included an example diff below [1].

We have a use-case beyond debugging in which we read telemetry every few 
milliseconds. From a performance point of view, adding the 2 additional 
endpoints would be very beneficial.

Thanks,
Kevin

[1]

diff --git a/lib/eal/common/eal_common_lcore.c 
b/lib/eal/common/eal_common_lcore.c
index 210636d21d..94ddb276c5 100644
--- a/lib/eal/common/eal_common_lcore.c
+++ b/lib/eal/common/eal_common_lcore.c
@@ -569,6 +569,32 @@ handle_lcore_info(const char *cmd __rte_unused, 
const char *params, struct rte_t
         return rte_lcore_iterate(lcore_telemetry_info_cb, &info);
  }

+static int
+lcore_telemetry_busy_cycles_cb(unsigned int lcore_id, void *arg)
+{
+       struct rte_tel_data *d = arg;
+       struct rte_lcore_usage usage;
+       rte_lcore_usage_cb usage_cb;
+       unsigned long cycles = 0;
+
+       memset(&usage, 0, sizeof(usage));
+       usage_cb = lcore_usage_cb;
+       if (usage_cb != NULL && usage_cb(lcore_id, &usage) == 0)
+               cycles = usage.busy_cycles;
+
+       return rte_tel_data_add_array_u64(d, cycles);
+}
+
+static int
+handle_lcore_busy_cycles(const char *cmd __rte_unused,
+               const char *params __rte_unused, struct rte_tel_data *d)
+{
+       int ret = rte_tel_data_start_array(d, RTE_TEL_U64_VAL);
+       if (ret)
+               return ret;
+       return rte_lcore_iterate(lcore_telemetry_busy_cycles_cb, d);
+}
+
  RTE_INIT(lcore_telemetry)
  {
         rte_telemetry_register_cmd(
@@ -577,5 +603,8 @@ RTE_INIT(lcore_telemetry)
         rte_telemetry_register_cmd(
                         "/eal/lcore/info", handle_lcore_info,
                         "Returns lcore info. Parameters: int lcore_id");
+       rte_telemetry_register_cmd(
+                       "/eal/lcore/busy_cycles", handle_lcore_busy_cycles,
+                       "List of busy cycle values. Takes no parameters");
  }
  #endif /* !RTE_EXEC_ENV_WINDOWS */