> From: Robin Jarry [mailto:rja...@redhat.com]
> Sent: Monday, 28 November 2022 10.00
>
> Allow applications to register a callback that will be invoked in
> rte_lcore_dump() and when requesting lcore info in the telemetry API.
>
> The callback is expected to return the number of CPU cycles that have
> passed since application start and the number of these cycles that were
> spent doing busy work.
>
> Cc: Bruce Richardson <bruce.richard...@intel.com>
> Cc: Jerin Jacob <jer...@marvell.com>
> Cc: Kevin Laatz <kevin.la...@intel.com>
> Cc: Konstantin Ananyev <konstantin.v.anan...@yandex.ru>
> Cc: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
> Cc: Morten Brørup <m...@smartsharesystems.com>
> Signed-off-by: Robin Jarry <rja...@redhat.com>
> ---
> v1 -> v2:
>
> Changed the approach based on Morten's review: the callback is now
> expected to report the total number of cycles since application start
> and the amount of these cycles that were spent doing busy work. This
> will give more flexibility in external monitoring tools to decide the
> sample period to compute busyness ratio.
>
> lib/eal/common/eal_common_lcore.c | 31 ++++++++++++++++++++++++++++---
> lib/eal/include/rte_lcore.h | 29 +++++++++++++++++++++++++++++
> lib/eal/version.map | 1 +
> 3 files changed, 58 insertions(+), 3 deletions(-)
>
> diff --git a/lib/eal/common/eal_common_lcore.c
> b/lib/eal/common/eal_common_lcore.c
> index 8a6c12550238..51f53fc93ece 100644
> --- a/lib/eal/common/eal_common_lcore.c
> +++ b/lib/eal/common/eal_common_lcore.c
> @@ -2,6 +2,7 @@
> * Copyright(c) 2010-2014 Intel Corporation
> */
>
> +#include <inttypes.h>
> #include <stdlib.h>
> #include <string.h>
>
> @@ -420,11 +421,20 @@ rte_lcore_iterate(rte_lcore_iterate_cb cb, void
> *arg)
> return ret;
> }
>
> +static rte_lcore_usage_cb lcore_usage_cb;
> +
> +void
> +rte_lcore_register_usage_cb(rte_lcore_usage_cb cb)
> +{
> + lcore_usage_cb = cb;
> +}
> +
> static int
> lcore_dump_cb(unsigned int lcore_id, void *arg)
> {
> struct rte_config *cfg = rte_eal_get_configuration();
> - char cpuset[RTE_CPU_AFFINITY_STR_LEN];
> + char cpuset[RTE_CPU_AFFINITY_STR_LEN], usage_str[256];
> + uint64_t busy_cycles, total_cycles;
> const char *role;
> FILE *f = arg;
> int ret;
> @@ -444,11 +454,19 @@ lcore_dump_cb(unsigned int lcore_id, void *arg)
> break;
> }
>
> + busy_cycles = 0;
> + total_cycles = 0;
> + usage_str[0] = '\0';
> + if (lcore_usage_cb && lcore_usage_cb(lcore_id, &busy_cycles,
> &total_cycles) == 0) {
The DPDK coding convention is to explicitly compare to NULL, i.e.:
if (lcore_usage_cb != NULL && lcore_usage_cb(...
> + snprintf(usage_str, sizeof(usage_str), ", busy cycles
> %"PRIu64"/%"PRIu64,
> + busy_cycles, total_cycles);
Consider adding the percentage here, for easy human consumption:
", busy cycles %"PRIu64"/%"PRIu64" (%.02f%%)",
busy_cycles, total_cycles,
busy_cycles ? (float)busy_cycles / (float)total_cycles * (float)100);
On the other hand, it is the average over the total uptime, so the percentage
might only be useful for very few cases.
> + }
> ret = eal_thread_dump_affinity(&lcore_config[lcore_id].cpuset,
> cpuset,
> sizeof(cpuset));
> - fprintf(f, "lcore %u, socket %u, role %s, cpuset %s%s\n",
> lcore_id,
> + fprintf(f, "lcore %u, socket %u, role %s, cpuset %s%s%s\n",
> lcore_id,
> rte_lcore_to_socket_id(lcore_id), role, cpuset,
> - ret == 0 ? "" : "...");
> + ret == 0 ? "" : "...", usage_str);
> +
> return 0;
> }
>
> @@ -486,6 +504,7 @@ lcore_telemetry_info_cb(unsigned int lcore_id, void
> *arg)
> {
> struct lcore_telemetry_info *info = arg;
> struct rte_config *cfg = rte_eal_get_configuration();
> + uint64_t busy_cycles, total_cycles;
> struct rte_tel_data *cpuset;
> const char *role;
> unsigned int cpu;
> @@ -519,6 +538,12 @@ lcore_telemetry_info_cb(unsigned int lcore_id,
> void *arg)
> 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);
> + busy_cycles = 0;
> + total_cycles = 0;
> + if (lcore_usage_cb && lcore_usage_cb(lcore_id, &busy_cycles,
> &total_cycles) == 0) {
Same comment about coding convention:
if (lcore_usage_cb != NULL && lcore_usage_cb(...
> + rte_tel_data_add_dict_u64(info->d, "busy_cycles",
> busy_cycles);
> + rte_tel_data_add_dict_u64(info->d, "total_cycles",
> total_cycles);
> + }
>
> return 0;
> }
> diff --git a/lib/eal/include/rte_lcore.h b/lib/eal/include/rte_lcore.h
> index 6938c3fd7b81..dc352297bcbc 100644
> --- a/lib/eal/include/rte_lcore.h
> +++ b/lib/eal/include/rte_lcore.h
> @@ -328,6 +328,35 @@ typedef int (*rte_lcore_iterate_cb)(unsigned int
> lcore_id, void *arg);
> int
> rte_lcore_iterate(rte_lcore_iterate_cb cb, void *arg);
>
> +/**
> + * Callback to allow applications to report CPU usage.
> + *
> + * @param [in] lcore_id
> + * The lcore to consider.
> + * @param [out] busy
> + * The number of busy CPU cycles since the application start.
> + * @param [out] total
> + * The total number of CPU cycles since the application start.
> + * @return
> + * - 0 if both busy and total were set correctly.
> + * - a negative value if the information is not available or if any
> error occurred.
> + */
> +typedef int (*rte_lcore_usage_cb)(
> + unsigned int lcore_id, uint64_t *busy_cycles, uint64_t
> *total_cycles);
> +
> +/**
> + * Register a callback from an application to be called in
> rte_lcore_dump()
> + * and the /eal/lcore/info telemetry endpoint handler.
> + *
> + * Applications are expected to report the amount of busy and total
> CPU cycles
> + * since their startup.
> + *
> + * @param cb
> + * The callback function.
> + */
> +__rte_experimental
> +void rte_lcore_register_usage_cb(rte_lcore_usage_cb cb);
> +
> /**
> * List all lcores.
> *
> diff --git a/lib/eal/version.map b/lib/eal/version.map
> index 7ad12a7dc985..30fd216a12ea 100644
> --- a/lib/eal/version.map
> +++ b/lib/eal/version.map
> @@ -440,6 +440,7 @@ EXPERIMENTAL {
> rte_thread_detach;
> rte_thread_equal;
> rte_thread_join;
> + rte_lcore_register_usage_cb;
> };
>
> INTERNAL {
> --
> 2.38.1
>
Looks good to me.
And we could probably discuss naming forever... "Usage" and "utilization" are
synonyms, but usage is shorter, so let's stick with that.
Acked-by: Morten Brørup <m...@smartsharesystems.com>
